As hot as it was on Thursday, Toronto didn't shatter the all-time heat high but did break the daily temperature record with a sweltering 38 C recorded by late afternoon, with a humidex making it feel more like 48 C.

Toronto's daytime high on Thursday broke the July 21, 1955 record of 35. 6 C and other cities in the region, like Windsor, Hamilton and Collingwood, all broke daytime high records as well.

The highest overall temperature, set in 1936 by a weather station at the University of Toronto, was 40.6 C for three consecutive days.

Environment Canada's Dave Philips said he blames the soaring temperatures on the heat dome.

The heat dome, a hot, stagnant high-pressure area, is pushing the jet stream well to the north and keeping cooler or wetter weather out of the region.

"There are going to be records falling all over today, because of this incredible heat dome," Phillips told CTV's Canada AM on Thursday.

"It is almost like a bully. It just doesn't move, you can't move it. Any kind of cold, fresh Canadian waves are blocked from coming in."

By Thursday morning, the heat dome forced temperatures to their highest mark in more than 170 years.

Phillips said the city reached an early morning temperature of 26.6 Celsius, a mark higher than any day since temperature started being recorded in the 1840s.

The previous morning high was 26.3 C, set on Aug. 1, 2006.

Environment Canada also issued a weather warning for most of southern Ontario, stating that an oppressive humidity could push humidex values well into the 40s through the afternoon.

Phillips said the heat wave is expected to continue at least until Sunday or Monday, when the city is finally expected to see some sparse splashes of rain. Even then, he says central Canada is expected to suffer through above average temperatures for the rest of the summer.

The night also offered no reprieve from steamy temperatures with several communities setting records for their hottest nights ever on Wednesday.

In Toronto, it only made it down to 26.6 C overnight.

Environment Canada said other communities, such as London and Hamilton also saw their hottest nights ever.

Thursday's high fell shy of the Canadian record of 45 C, set in Midale and Yellow Grass Sask., in 1937.

Extreme heat alert continues

An extreme heat alert issued by the City of Toronto extended into Thursday, as health officials were warning city residents that the high temperatures could be treacherous for at-risk adults, seniors and the homeless.

An extreme heat alert is declared when the risk of heat-related death in the city is 50 per cent higher than what it would be on a day without a heat alert, according to Toronto Public Health.

The city has opened seven cooling centres across the city and extended hours at nine pools.

The public is encouraged to call or visit family and friends who are at a greater risk of suffering from heat-related illnesses, such as isolated adults and seniors.

St. John Ambulance said heatstroke can result in permanent brain damage if not treated seriously. If you or someone you know suffers from a rapid pulse, weakness and flushed skin, that person should call for medical assistance and seek a cool, shaded place to rest.

No record for power consumption: watchdog

Despite the fuss over Ontario's record-breaking heat wave, the province's power watchdog says it won't be breaking any electricity demand records.

With air conditioners working overtime, the Independent Electricity System Operator predicts Thursday's power consumption will fall well short of the record books.

Thursday's peak demand is predicted to hit 25,591 megawatts, below the all-time high of 27,005 megawatts set on Aug. 1, 2006.

IESO spokesman Terry Young said lower industrial demand is behind the comparably lower power use. Young added that conservation efforts are paying off, with many residents moving their electricity use to off-peak hours after 7 p.m.

Heat wave telephone scam

Durham regional police say that not everyone is acting altruistically during the recent heat wave.

Officials are warning residents of a telephone scam offering a bogus hydro saving device. Police say an aggressive telemarketer has been calling Durham Region residents and offering a $150 widget they say will cut hydro rates by 60 per cent.

Hydro officials say they are not involved in selling such products and ask anyone who is contacted to call police.

With files from The Canadian Press