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This latest heat wave in eastern Ontario and western Quebec is expected to be at its most punishing on Tuesday and bring the hottest temperature of the year so far to some places.
Tuesday’s highs are forecast to be in the mid-30s with humidity around the low 40s. That temperature is expected to stay above 20 C overnight with lingering humidity.
Ottawa’s forecasted high of 35 C would be the hottest day of 2026 so far. It, among with other hubs such as Brockville and Kingston, could set daily heat records.
Environment Canada first issued heat warnings for the region on Sunday afternoon. Monday peaked around 30 C in Ottawa late in the afternoon with humidity making it feel like 35.
The warnings are expected to end on Wednesday as temperatures and humidity slowly ease.
Many municipalities such as Ottawa offer lists and/or maps of public places to cool off, which may included dedicated cooling centres.
People should be on the lookout for signs of heat exhaustion, which include headaches, dizziness, thirst and fatigue, the weather agency said.
Anyone who is showing signs of heat stroke should call 911, they added.
The heat is contributing to an extreme fire risk in the Pontiac and some local parts of Algonquin Park. Risks are considered very high or high elsewhere, with restrictions in place including a western Quebec burn ban.
Thunderstorm watch in Outaouais
Western Quebec is also under a severe thunderstorm watch Tuesday afternoon and evening.
Risks include a tornado, wind, hail and heavy rain along with lightning.
A tornado watch or warning would come if the possibility of a tornado increases.
All local alerts are yellow, the lowest and most common level of Environment Canada’s three-colour scale it introduced in 2025.