A heat warning spanning much of eastern Ontario has residents ducking into air conditioned buildings, while others slip into nearby lakes and rivers to cool down on the hottest July 5 on record for the Ottawa region.

The mercury reached 33.7 degrees Celsius on Monday, with the humidex making it feel more like 45. The previous record of 32.8 degrees Celsius was set in 1976.

Forecasters are expecting temperatures to reach highs of 34 degrees until Thursday. The normal maximum for July 5 in Ottawa is about 26 degrees Celsius, according to Environment Canada.

"It's going to be hot, pretty steamy, in the next few days," said CTV Ottawa's weather specialist J.J. Clarke.

"The coolest day we have in our five-day forecast, by the way, is coming up on Friday. On Friday, we're talking about a cool high of 28 degrees. Until then, it's going to be nice and warm."

Heat warning

The warm weather prompted Ottawa's chief medical officer of health to issue a heat warning Monday until further notice. The city automatically declares a heat warning when Environment Canada forecasts a humidex of 40 or more for at least two days in a row.

The heat is especially difficult for the elderly and those with chronic illness, said Dr. Isra Levy. He adds infants, young children, the homeless and those who take certain types of medications, such as antidepressants, are also at greater risk.

If residents get too much heat exposure, they risk suffering dehydration, heat exhaustion or heat stroke. In extreme cases, people can die.

Residents looking to beat the heat are advised to:

  • Drink plenty of fluids, preferably water. It's also best to avoid caffeine and alcohol
  • Avoid strenuous physical activity outdoors
  • Avoid direct exposure to sunlight and seek shade
  • Wear light and loose clothing
  • Spend at least two hours in an air-conditioned location. This can be a shopping mall, library, movie theatre or neighbourhood community centre
  • Never leave children, the elderly or pets in an unattended vehicle. Even with the windows rolled down; it is not safe

Ottawa paramedics say those who don't have access to air conditioning should cool down with fans, wet compresses, cool showers or baths.

Ottawa Public Health is also encouraging residents to visit family, friends and neighbours who may be vulnerable to the heat.

Empty patios, busy pools

While hot weather usually brings throngs of people to the Byward Market, downtown patios were unusually empty Monday afternoon.

"It does get to that point where it gets too hot and people just don't want to be outside. It's just too muggy, they'd rather sit inside in the air conditioning," said Shauna Bradley, of The Druid restaurant.

While patios were empty, wading pools and beaches across the city were packed. Both Westboro and Britannia beaches reopened Monday following a no-swimming advisory due to high levels of E.coli.

While Toronto reported large power outages, in Ottawa about 2,000 customers lost power in Stittsville. Hydro Ottawa said only 1,000 customers remained without power at the dinner hour and power was expected to be restored shortly.

Hot summer ahead

For those worried this might be the only hot week of summer, Environment Canada climatologist David Phillips says it looks like Ontario has more warm weeks ahead.

"This is just the beginning of maybe a three-act play," Phillips said Monday.

"We think this summer will be warmer than normal. Even when this ends people shouldn't say ‘Oh my gosh, all of the good summer was in the first week of July, I should have taken my holidays.'

"There will be other moments when we'll be blessing and cursing this weather."

Smog advisory

The warm temperatures have also resulted in smog advisories for some places in eastern Ontario.

A smog advisory went into effect Sunday for: Bancroft - Bon Echo, Belleville - Quinte - Northumberland, Kingston - Prince Edward, and Stirling - Tweed - South Frontenac.

Residents in those areas are urged to reduce the number of car trips they take by opting to ride the bus or car pool. They are also asked to avoid the use of gas-powered engines such as lawn mowers and chain saws.

With files from CTV Ottawa's Vanessa Lee and CTV.ca News Staff