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Southern and Eastern Ontario will be slammed with “dangerously hot” temperatures for at least the next few days.

Environment Canada issued its first significant heat warning of the season on Saturday, saying hot and humid conditions will begin in the province’s far south, including Windsor, and will likely continue until Wednesday.

Areas a bit further north, including Toronto and eastern Ontario, are expected to feel the heat on Sunday.

Daytime highs are forecast to hit 31 C to 36 C, with the humidex making it feel more like 40-50 degrees.

The weather agency says a cold front is expected to push through late Tuesday, but noted it’s uncertain how far south it will reach.

It says that could mean the higher temperatures extend into Wednesday in southwestern Ontario.

People are encouraged to stay hydrated by drinking water before they’re thirsty and to watch for early signs of heat exhaustion.

Teachers and families, are you worried about the heat wave hitting schools? Send us your thoughts

Environment Canada’s seasonal forecast says the summer is expected to be hotter and more humid than normal across Ontario.

Studies have shown human-caused climate change, driven by the burning of fossil fuels, is increasing the likelihood and length of Canada’s heat waves.

Meanwhile, the agency is also warning residents of British Columbia’s southern Interior of possible heavy rain and thunderstorms as flood risks rise in the region.

The weather agency says areas including the Fraser Canyon, the Okanagan, Kamloops and parts of the Shuswap could see overall rainfall of up to 40 millimetres, along with “heavy showers with embedded thunderstorms.”

Environment Canada says the precipitation could create localized flooding as well as landslides in areas with vulnerable landscapes such as those burned by past wildfires.

The same weather system is also forecasted to bring possible wet snow over higher elevations, and motorists on the Coquihalla, Okanagan Connector and Highway 3 are asked to be cautious.

B.C.’s River Forecast Centre has placed some southeastern parts of the province along the Alberta border, including Cranbrook, Invermere and Golden, under a flood watch.

The Okanagan, Shuswap and Kamloops, meanwhile, are under a high streamflow advisory, with a possible rapid rise to river levels and minor flooding of low-lying areas.