The Weather Network has forecasted that on both Saturday and Sunday, it's going to reach a high of °C, which will feel more like 43°C with the humidex.
Environment Canada says the "most significant heat wave in the past few years" will grip Ottawa and all of southern Ontario over the next week.
The temperatures will be "sultry" and "oppressive", he told CTV Barrie on Thursday. Overnight low temperatures are expected to be in the low to mid twenties, providing little or no relief from the heat.
Phillips suggests the more heat-sensitive of the population take it easy.
It could be the hottest weather event of the season and because of the intensity of the weather situation, heat warnings are likely to be issued in the afternoons. "This heat wave will persist through next week".
The health unit advises people to prepare for the heat by staying hydrated, staying cool, and to check air quality.
High humidity makes the weather seem hotter than it would on a dry day, and the perspiration from the heat can not be evaporated as easily on a humid day.
Heatwave response: Families are being advised to take special care of the youngest and oldest members of the family during the next five straight days of heat and humidity Environment Canada is predicting.
It says "a very warm and humid airmass" will settle over eastern Quebec and the Maritime provinces this weekend, and will last into next week.
Current forecasts expect temperatures to be over 30 C for all of next week.
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