Potentially lengthy heat warning issued for most of eastern Ontario

13-Jul-2025

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A heat warning has been issued for communities such as Ottawa, Gatineau, Kingston and Cornwall as Environment Canada expects a wave of hot, humid temperatures that could last up to a week.

The weather agency issued the alert at late Friday morning for most of eastern Ontario, plus Gatineau and the Grenville-sur-la-Rouge area of western Quebec. No alerts are in place for Renfrew and Prince Edward counties, nor the Bancroft area.

Eastern Ontario and Gatineau's alert said daytime highs are expected to range from 29 to 32 C and with humidity, feel like 35 to 40. Nighttime lows may not dip far below 20 C which means little relief from sweaty conditions.

It's anticipated that Saturday will feel the hottest. Ottawa's forecasted high that day is 31 C and its overnight low Saturday into Sunday is 22 C, plus humidity. It could be Thursday before it cools off, according to the alert, though forecasts get less certain the further into the future they delve.

The Grenville-sur-la-Rouge area's heat warning may end Monday. The rest of western Quebec has a special weather statement about weather that's expected to be very slightly cooler on July 11 and July 12.