Much of southern Ontario is under a heat warning as a two-day heat event is expected this weekend.

Environment Canada has issued heat warnings for a stretch of the province from Cornwall to Barrie and southwest to Windsor.

Maximum temperatures are expected to reach or surpass 30 C and hit the low forties when combined with humidity.

The weather agency says minimum temperatures in the low to mid-twenties are expected, bringing little relief from the heat.

Cooler temperatures are forecast for Monday.

Residents are advised to drink plenty of water even before feeling thirsty, to stay in a cool place and check on older family, friends and neighbours to ensure they are staying hydrated and cool.