Why night-time heat can be deadly

It’s not just daytime heat in the summer that can be deadly — a rising trend in night-time temperatures is also raising health concerns.

Over the past five decades, the average minimum temperature in July has gone up from 13.7 C to 16.4 C, according to Environment Canada.

Those figures don’t appear deadly on the surface. But they show a dramatic trend that the night-time temperatures in Toronto are definitely getting warmer during the summer, says Dave Phillips, senior climatologist with Environment Canada.

 “There is more and more evidence that climate change is about night-time warming rather than day-to-day heat,” said Phillips.

And that may bring big trouble. If you overheat and have no way of cooling down you can suffer from heat exhaustion. In more severe cases, it can lead to heat stroke, which if not treated immediately, can be fatal.

Usually, the body is able to cool down through evaporation of sweat on the skin. But in cases of extreme heat or high humidity the body can’t do this.

The phenomenon of higher evening temperatures most likely occurs because “heat absorbed throughout the day by dark structures and surfaces in the city is released overnight, preventing the city from cooling off,” according to a recent Toronto Public Health report.

 “Having the opportunity to cool off, even for a few hours, is critical in preventing heat-related illness and death.”

The report, presented to the Toronto Board of Health earlier this week, adds that “the daily minimum temperatures are increasing faster than the average or maximum temperatures.”

That trend is something Toronto Public Health is concerned about. “Higher night temperatures can have an effect on the ability to cope with the heat,” said Elaine Pacheco, a manager with Toronto Public Health.

 “In the evening, if temperatures cool down significantly, especially in an extended heat wave, people have an opportunity to get relief from the day time high,” she said.

In Europe in 2005 and Chicago in 1995 hundreds of people died during heat waves. The problem then was the night time temperatures didn’t fall, said Phillips. Even those in good health succumbed to the high temperatures. There simply wasn’t any relief.

There will be more of the same in the years to come says Phillips. In fact, the difference between daytime highs and night-time lows in the summer is slowly shrinking.

In addition, the dew point – a measurement of humidity – is increasingly elevated at night, which means your body is not able to perform as its engineered to do – get rid of natural heat and cool off, said Phillips.

Some nights earlier this summer the dew point was 23 C or 24 C during the day and even when the temperature dipped to 25 or 14, the dew point remained the same. “That’s unbelievable,” said Phillips.

“It’s like being in Savannah, Georgia rather than Phoenix, Arizona.”

Traditionally, the difference between a daytime high and night-time low in Toronto was quite wide with a high of about 28 C and a low of 15 or 16 C.

But during the latest heat wave, the daytime high reached about 35 C and the night time low only dipped to 25 C. That just doesn’t offer any relief — especially for people who don’t have air conditioning.

Phillips ran some data for the Star to illustrate the shrinking range. The difference in the 1960s was about 12.7 degrees; in 2000, it was 10.6 degrees. “This is clearly how the thermal climate in Toronto in the summer is changing.”

According to the Environment Canada data from Pearson Airport, in the 1960s there were 168 days in July where the temperature was over 30 C. Between 2000 and 2009, there were 189. 

But the next set of numbers is alarming, he said. In the 1960s there were only 21 nights where the minimum temperature in July was over 20 C. But from 2000 to 2009, that number rose to 109.

And that phenomenon is not just occurring in Toronto, but across many parts of the world, he said.

“Over the past 130 years night-time minimum temperatures are increasing,” said Pacheco. The rise in night-time temperatures is not the only factor that affects people in a heat wave, she said, “but it’s more significant when there is an extended heat event.”

Her advice for those that don’t have air conditioning is to take cool showers, baths, mist themselves with cold water, drink lots of water, minimize the actual time outdoors, close blinds and drapes to block out the sun, avoid using the oven, visit a place with air conditioning so you can get some relief.

--Debra Black, Staff Reporter

City of Toronto issues the sixth heat alert of the season

Those who have this Simcoe Day off can look forward to a hot one: the City of Toronto has issued a heat alert today.

Temperatures will climb to 33 C today, but will feel more like 37 C. There’s also a piping UV index of 9, or very high, according to Environment Canada.

Toronto Public Health staff monitors its heat health alert system to determine whether a heat alert should be issued . The system compares forecast data to historical weather conditions which have led to increased mortality in Toronto in the past.

Factors taken into consideration include conditions like temperature, dew point, humidity, cloud cover, wind speed and direction.

This is the city’s sixth heat alert of 2011. July was the hottest July on record for the City of Toronto with an average temperature of 24.37, according to Dave Phillips, a climatologist with Environment Canada. That beat out the previous record of 24.3 in 1999.

And the warmest day the city has ever seen was this past July 21, when the mercury rose to 37.9 C. The average temperature for the day was 32 C, which beat out a previous record of 31.5 C on Aug. 1, 2006.

“If you stuck a thermometer in Toronto this past July, it would say well done,” Phillips said.

The warmest temperature ever recorded at Pearson was 98.3 on Aug. 25, 1948.

At the rate we’re going, this summer may beat out the summer of 1955 as the hottest Toronto has ever seen. August is expected to mirror the record-setting July we just had, which was not only the hottest July, but also hotter than any June of August the city has ever seen, according to Phillips.

The average temperature for July and August combined in 1955 was 23.6 C. “We are now at 24.4 C, so we could be a degree cooler in August and still break that record,” he said.

July was certainly one for the books in more ways than one. There were 16 days where the average temperature hit above 30 C, and we usually only have 6. We had 30 hours more of sunshine than average, and we only received 43 per cent of what we’d normally get in terms of precipitation—we had 32.4 mm of rain, when we normally have an average of 74.4. July dragged us through a 14 day dry spell as well.

“It was a scorcher. Toronto was well done, baked, grilled roasted.

“It was the hottest day ever, it was the hottest month ever, I mean, you run out of superlatives talking about this particular month.”

In recent memory, the hottest summer Toronto has seen was 2005. The average temperature for July that year was 24.1. That year also had a number of smog days, with 12.5 in July alone. Phillips said there were probably more than 30 smog days throughout the duration of that summer.

In 2005, there were 10 nights on which the temperature remained above 20 C, compared with the 12 we had last month, which brings us to a trend Phillips said is gaining momentum.

“What’s really different in Toronto these days is the warm nights. It’s a hot time in the old city.”

He chalks the sultry summer nights up to increased urban development.

“The city is just getting warmer and cloudier, there’s more heat being trapped in.”

In terms of heat this holiday Monday, Phillips said we shouldn’t rule out the possibility of a humidex advisory being issued. Right now the humidex sits at 37 C, and advisories are issued when it hits 40 C.

The city is urging people to drink lots of water, go to air conditioned spaces and try to stay out of the sun.

In stark contrast to the sweat bath we’re in now, the lowest average temperature for a Toronto summer on record is 17.7 C, and that was in 1965.

— Sarah Ratchford, Staff Reporter

Hot sun and warm temperatures greet parade-watchers and party-goers this weekend

Hot and sunny at Ashbridges Bay on a beautiful Saturday morning by Lake Ontario. Dave Cooper/Toronto Star

The thousands of Torontonians lining the streets for the Caribbean Carnival and parade could blister in the sun this holiday weekend, with high temperatures and a very high UV index.

The festival formerly known as Caribana kicks off Saturday morning at 10 a.m. with the Grand Parade starting from Exhibition Place.

• Photos: Sunny Saturday

About 20,000 masqueraders and musicians will dance and perform soca, calypso, reggae and salsa music down the 1.5-kilometre route on Lake Shore Blvd. W., which is closed from Strachan Ave. to Colborne Lodge Dr.

The weather is perfect for the weekend-long outdoor celebrations. With an expected high of 30 C and a UV rating of 9, or very high, and just a few clouds in the sky, forecasters are warning revelers to wear sunscreen to avoid a burn, especially between 11 a.m. and 4 p.m., when the sun is at its strongest.

“Extra precaution [is] required – unprotected skin will be damaged and can burn quickly,” Environment Canada warns on the weather office website.

The self-proclaimed largest Caribbean festival in North America, the 44th annual carnival is expected to attract more than a million participants for the weekend-long jam.

And as the party winds down Sunday evening, there is a slight risk, at 30 per cent, of rain or thundershowers in the forecast.

Zoe McKnight, Staff Reporter

Hundreds of Beach Volleyball players worked up a sweat on the sand and people strolled and cycled along the waterfront. DAVID COOPER / TORONTO STAR

Deadly Korean landslides bring landmine warning

South Korean soldiers shovel mud after a flood caused by heavy rains hit the area around an apartment complex in Seoul on Thursday. Tens of thousands of South Korean troops joined a massive clean-up after record-breaking rainfall killed dozens. (PARK JI-HWAN/AFP/Getty Images)

SEOUL, South Korea - Thousands of rescuers dug through thick mud for survivors of deadly landslides and flooding as South Korea's military warned Thursday that buried land mines may have slid down mountains weakened by rain.

Massive rainfall in Seoul and surrounding areas since Tuesday has killed at least 47 people, and another four were missing. The rain stopped or decreased Thursday, but more was forecast until Friday morning.

At a mountain where a deadly slide hit Wednesday, digging for missing people was halted Thursday until the rain stopped because the Defence Ministry said mines placed there in the 1960s could have shifted. Soldiers with metal detectors were waiting to search for the mines, said Yoon Yong-sam, a spokesman for the air force, which planted the land mines around an air defence base on the mountain.

A defence ministry official said earlier that 10 mines could have been pushed down Wumyeon Mountain. The official declined to be named because of policy. Another ministry official, spokesman Kim Min-seok, played down the immediate risk because a concrete wall on the hillside could be stopping the mines from reaching rescue workers.

South Korea's military dug up many land mines on the mountain between 1999 and 2006, but about 10 couldn't be accounted for, officials said. Fences around the base have warnings about unaccounted land mines.

There were also fears of land mines in northern provinces also hit by flooding and slides, prompting the Joint Chiefs of Staff to order mine-search operations where needed.

The landslide Wednesday in southern Seoul killed at least 16 people. About 5,000 firefighters, soldiers, police officers and others mobilized Thursday to try to find any survivors and clean walls of mud piled in residential areas near the base of the mountain, emergency official Kim Wu-min said.

Bae Jin-sun, a 27-year-old who works in southern Seoul, said she was worried about the safety of rescue workers near the mountain.

"There is still the possibility of a land mine falling through the cracks," she said.

Footage by YTN television network showed excavators removing a mass of mud and fallen tree parts and rescuers in raincoats shovelling up the dirt piled up near an apartment. Uniformed soldiers and firefighters wearing cotton gloves used their hands to pull out rocks and tree branches from the mud.

Another landslide early Wednesday killed 10 college students sleeping in a resort cabin in Chuncheon, north of Seoul. The students from Inha University in Incheon, just west of Seoul, were volunteering at a local elementary school.

The National Emergency Management Agency reported 18 more deaths because of a stream flooding and landslides elsewhere in towns near Seoul. No deaths of foreigners have been reported.

The rainfall left almost 5,000 people homeless, flooded about 1,380 houses and caused power outages at more than 125,000 homes throughout the country, the National Emergency Management Agency said in a statement Thursday.

The 17 inches (440 millimeters) of rain that fell on Seoul on Tuesday and Wednesday was about 15 times more than the average two-day rainfall at this time of year, according to the state-run Korea Meteorological Administration.

-- The Associated Press

Vehicles are submerged in floodwater after heavy rain in Seoul on Thursday.(AP Photo/Ahn Young-joon)

People work to restore a road damaged by a landslide in Seoul on Thursday. South Koreans were cautioned about rogue landmines and explosives after a series of deadly landslides in and around the capital Seoul swamped military sites. (REUTERS/Truth Leem )

Thousands of rescuers used heavy machinery and shovels Thursday to clear mud and search for survivors. (AP Photo/Ahn Young-joon)

South Korean soldiers remove debris at a damaged apartment. (AP Photo/Bae Jung-hyun, Yonhap)

River of mud buries sleeping students in Korean landslide

A street in Seoul after torrential rain pounding South Korea triggered landslides that killed dozens of people. (JANG SEUNG-YOON/AFP/Getty Images)

SEOUL, South Korea - Walls of mud barrelling down a hill buried 10 college students sleeping in a resort cabin and flash floods submerged the streets and subway stations in Seoul, killing at least 32 people Wednesday in South Korea's heaviest rains this year.

The students were engulfed by a landslide in Chuncheon, about 68 miles (110 kilometres) northeast of Seoul, said fire marshal Byun In-soo. A married couple and a convenience store owner also died.

Witnesses interviewed on television said the landslide sounded like a massive explosion or a freight train. They described people screaming as buildings were carried away by rivers of mud.

About 670 firefighters, soldiers, police and others rushed to rescue those trapped and extract the dead from the mud and wreckage in Chuncheon, where 24 others were injured and several buildings destroyed.

In southern Seoul, 16 people died when mud crashed through homes at the foot of a mountain, the National Emergency Management Agency said. Three others also died after a stream just south of the capital flooded, and 10 people were reported missing throughout the country, the agency said in a statement.

Fast-moving mudwaters filled the streets in Seoul on Wednesday, sending residents scrambling to the roofs of their partially submerged cars.

Water filled some subway stations and spewed from sewers. TV images showed people in one flooded subway station using shovels, brooms and a wooden board in an effort to keep more rain from coming in.

Footage showed officials rescuing hikers stranded on mountainsides. People plodded down streets covered with knee-deep water, many barefoot, their pants rolled up. In Seoul's centre, cars were restricted from entering the lower part of a submerged two-level bridge.

The heavy rain since Tuesday left about 620 people homeless and flooded 720 houses and about 100 vehicles throughout South Korea, the emergency management agency said.

About 17 inches (440 millimeters) of rain fell on Seoul and more than 13 inches (340 millimeters) on Chuncheon in the last two days, about 15 times more than the average two-day rainfall at this time of year, according to the state-run Korea Meteorological Administration.

Weather officials said another 10 inches (254 millimeters) could fall in northern South Korea, including Seoul, through Friday.

The Seoul Metropolitan Police Agency issued a traffic emergency, mobilizing more officers to deal with the inclement weather.

Seoul, a bustling capital of 10 million, shut down portions of two major highways stretching along each side of the main Han River because of high water levels, said disaster official Kim Ji-hwan.

A dam located just east of Seoul was discharging 16,400 tons of water per second, said Cha Jun-ho from the Han River Flood Control Office. The dam already discharged about 1,000 tons per second days before the recent downpours.

People in Seoul, where smartphones are ubiquitous, posted dozens of photos on Twitter and Facebook showing inundated streets and mud-covered cars. Many complained online that Seoul had neglected to prepare for the downpours.

--The Associated Press

People try to climb on top of a car on a submerged road in Seoul. (AP Photo/Yonhap)

Damaged cars are seen at a village after a landslide and heavy rainfall in Seoul July 27, 2011. (REUTERS/Park Mun-ho/Newsis)

Rescue workers and residents try to escape floodwaters after a river burst its banks following heavy rains in Gwangju, about 40 km southeast of Seoul. (REUTERS/Kang Jong-Min/Newsis )

South Korean soldiers begin the clean-up in Seoul. (Photo by Chung Sung-Jun/Getty Images)

Cars are submerged by floodwaters along a Seoul street. (Photo credit should read YANG HOE-SEONG/AFP/Getty Images)

South Korean rescue workers in Seoul. (AP Photo/Yonhap, Kim Ju-sung)

July’s been dry, but it’s not a record-breaker

Despite an arid stretch with scorching temperatures in the 30s, Toronto did not break the record for the driest July.

The record was set in 1957 with 11.4 mm of rain, but that mark was passed on Saturday evening alone, when four hours of showers delivered 13.2 mm.

Prior to Saturday, the city had received a mere 4.4 mm of rain in the entire month.

The showers were followed by a three-hour thunderstorm early Monday, which caused several power outages throughout the city.

However, the rainfall tally since the start of the month remains well below the July average of 74.4 mm.

“In a cool, dry month, it wouldn’t have been nearly as noticeable,” said Dave Phillips, senior climatologist at Environment Canada.

Phillips called this morning’s storm “the million dollar rain.”

“I know I got soaked this morning walking from the GO train to my office,” he said, “but I couldn’t care less.”

Monday’s storm also brought cooler weather to Toronto, prompting the city to cancel an extreme heat alert that was posted five days ago.

Phillips says a weak cold front came through the city on Sunday, bringing the humidex values down to the low 30s — relatively comfortable weather compared with muggy air we were experiencing last week.

“People must have felt they were in the Caribbean,” he said.

While the rain will provide some moisture for dehydrated vegetation, it won’t give us green lawns, Phillips said.

“We need a monsoon to solve the problem and this is not a monsoon,” he said, adding that the recent storm is not a trend but isolated activity.

More showers are expected throughout Monday with an expected high of 28 C.

There is also 30 per cent chance of showers Tuesday and a possibility of rain Thursday but the forecast for upcoming long weekend looks dry and sunny, with temperatures in the low 30s.

- Amanda Kwan, with files from Aleysha Haniff

Tornado warnings called off

All tornado warnings for southwestern Ontario have ended.

Tornado warning issued for parts of southwestern Ontario

Environment Canada is warning people to that tornados could hit overnight Saturday tonight in parts of southwestern Ontario.

Areas that could be affected include Strathroy, Komoka, Western Middlesex County, Eastern Middlesex County, London, Watford, Pinery Park, Eastern Lambton County, Woodstock, Tilsonburg, Oxford County, Simcoe, Norfolk, Delhi, Rodney, Shedden, Western Elgin County, and Parkhill.

People in these areas are advised to seek shelter immediately and carefully monitor conditions.

Heat alert extended

The extreme heat alert has been extended in Toronto as temperatures are expected to hit a scorching 34 C today, feeling more like 40 C with humidity.

This is the fourth day in a row that the city has been under an extreme heat alert.

To make matters worse, the city hasn’t seen substantial rainfall since July 3. There were light showers Friday night but it was “just a sprinkle” — not even enough to measure, according to Tony Cham, a meteorologist at Environment Canada.

Since the start of July, Toronto has seen only 4.4 mm of rain when the norm for this time of the year is about 74.4 mm.

The driest July ever was set in 1957 with 11.4 mm of rain.

Cham says it is hard to predict whether Toronto will break the record this year since there are still nine days left until the end of the month.

But relief may be in sight.

There is a 30 per cent chance of showers Saturday evening and a 60 per cent chance of rain Sunday night into Monday morning.

“There’s still some hope,” Cham said.

Meanwhile, to cope with the extreme heat, the city has opened cooling centres across Toronto and some city pools may extend their operating hours.

Much of the United States and Canada are trapped under a heat “dome” caused by a huge area of high pressure that’s compressing hot, moist air beneath it and keeping the jet stream well to the north.

This high-pressure system is leading to scorching temperatures like the ones Toronto saw Thursday when the mercury hit a sweltering 37.9 C, the highest July day temperature ever recorded at Pearson airport but just shy of the 38.3 C record set on August 25, 1948.

The smog that sometimes accompanies hot weather is nowhere to be seen, though. The city’s only had one smog day this summer. In 2005 — a similar year temperature-wise — there were 20 by this time.

There have been fewer smog days partly because of improved air quality, said Kate Jordan, a spokesperson for the Ontario Ministry of Environment.

In the past eight years, the province has seen reductions in fine particulate matter and nitrogen dioxide — the two main ingredients in smog, Jordan said. But weather also plays a role. “While we’ve had really warm and sunny weather, we haven’t had stagnant air pressure and the hazy conditions,” she said.

This is because the winds blowing through Toronto are not coming from the south, which typically brings in dirtier air and higher humidity, she adds.

 

Toronto's thirsty! City approaches record for driest July ever

After a parched, scorching month, it may turn out this was the driest July on record, forecasters say.

Observations at Pearson Airport indicate the city has seen no rain since July 3, and just 4.4 millimetres of rain in total fell in the last 4 weeks.

“That would be enough to keep the dust down and that’s it. Toronto hasn’t had a drink of water in 18 days,” said Dave Phillips, senior climatologist at Environment Canada.

The driest-ever July was in 1957, with 11.5 millimetres of precipitation. That means that the city would have to see a good 7 millimetres of rain before the end of the month, or risk breaking that bone-dry record.

What’s worse is that this heat-wave of a July, with its humidex advisories and recent extreme heat alerts, is making the need for water all the more pressing.

Although Thursday’s high, at 37 degrees, did not break the all-time record for a high temperature at Pearson, it was the hottest day of the year, the hottest July 21 on record, and the hottest day in the month of July ever recorded in Toronto.

“We’ve had less precipitation and the effects are much greater now because it’s been much hotter. A lot more days above 30, and the average temperature 2.2 degrees warmer than normal,” Phillips said.

But there could be relief in sight as Environment Canada reports a 30 per cent chance of showers early Saturday morning. Sunday might also be inclined to give us a break, with a 60 per cent chance of rain.

But that doesn’t mean you can let up on the sunscreen, as Saturday’s high is 35C and Sunday’s is 29C.

Sunday is expected to be cloudy, but Saturday will likely have a UV index of 9, or very high.

There have been 13 days in July logged at temperatures above 30. “So even if we get some rain between now and August 1, we probably would be in a worse dry situation [than 1957] come the end of the month,” he said.

Meteorologist Marie-Eve Giguere explained why summer thunderstorms are typically so common in southern Ontario.

To produce a storm, three elements are required. “You need moisture, which no doubt is in the air mass. And you need instability. So with the heat, you have an unstable air mass. You need a third thing, a trigger,” Giguere said.

Cold fronts typically provide the trigger, by pushing the warm, humid air up, creating clouds. But the minor cold front that moved in over the GTA yesterday was simply too weak to make it rain.

“It’s still pretty sultry and oppressive,” Phillips said. Friday’s high is expected to reach 35.

The weak cold front “wasn’t enough to trigger anything,” he said. The closest chance of rain is Monday, at just around 30 per cent.

Elsewhere in the province, firefighters are battling forest fires in northern Ontario that have forced thousands from their homes.

The province said 114 fires are burning over nearly 500,000 hectares of forest, mostly in the northwest.

The hot, dry conditions are making it difficult to stamp out the flames.

Zoe McKnight, Staff Reporter with files from the Canadian Press