TORONTO -- Environment Canada has issued a heat warning for much of southern Ontario, from Windsor through to Peterborough and Ottawa.

The agency says temperatures are expected to be high, and nighttime lows will provide little relief from the heat.

In Windsor, it's expected to reach at least 32 C Sunday and Monday, with lows near 22 C.

Environment Canada says Toronto's temperatures are expected to peak at 31 C Sunday, and 32 C Monday, with lows near 21 C.

And in Ottawa, highs are expected to be about the same as those in Toronto, with lows near 20 C.

Environment Canada is warning people to watch out for the effects of heat-related illness, including swelling, rash, cramps, fainting and the worsening of some health conditions.

It says people should drink plenty of water, even before starting to feel thirsty, and seek a cool place.

It's also reminding people not to leave pets in parked cars.