The high heat prompted Environment Canada to issue a weather warning for the region Thursday as temperatures soared across eastern Ontario and west Quebec.

The temperature in Ottawa at noon was 32 degrees Celsius with a humidex that made it feel more like 44. By 4 p.m., it was 35.8 degrees Celsius with a humidex that made it feel like 46.

Environment Canada says the extreme heat is due to a tropical air mass that is causing temperatures in many parts of the province to soar to the mid- to upper-30s. The humidex makes it feel even hotter.

But hot and humid weather can also be dangerous, causing dehydration, heat exhaustion, heat stroke and even death.

"Pay close attention because on a day like this, you can go from heat exhaustion to heat stroke within a few minutes if you keep pushing it," said JP Trottier, a spokesperson for Ottawa paramedics. "If you feel thirsty – drink. If you feel hot – get out of that sun."

Those most at risk in extreme heat are the elderly, chronically ill, infants, children and the homeless. People who take Parkinson's medication or anti-depressants are also at risk.

In Ottawa, the Salvation Army's outreach team worked extended hours to make sure clients were kept cool and well-hydrated.

"The homeless can be an extremely vulnerable population. They are affected by many different health concerns that can be exacerbated by the heat and the sun . . . psychiatric medication specifically can affect people in the heat and the sun," said Darren Graham, co-ordinator of the Salvation Army's outreach services.

While many people were able to escape the heat in air-conditioned workplaces Thursday, others weren't as lucky.

At Middle East Bakery on Somerset Street, workers were sent home when the temperature in the kitchen hit 58 degrees Celsius.

"In the summer it's just unbearable. So when the customers come in here and say, 'Oh, you must be awfully hot, oh you look so warm', I stop them in their tracks. We don't discuss the heat in here. Not until the beginning of the winter," said Jacqueline Jaber of Middle East Bakery.

To avoid heat-related illnesses people are advised to:

  • drink plenty of fluids, preferably water
  • avoid strenuous physical activity outdoors
  • avoid direct exposure to the sun
  • wear lightweight and loose clothing
  • spend at least two hours per day in an air-conditioned location

With a report from CTV Ottawa's Vanessa Lee and Katie Griffin