Elevated risk of strong thunderstorms today for southern Quebec

The National Weather Service severe weather outlook for Sunday. Strong to severe thunderstorms are likely this afternoon across southern Ontario and Quebec. (NWS Burlington)

A severe thunderstorm watch will likely be needed for a portion of southern Quebec including metro Montreal later today. If you have outdoor activities planned, stay alert to changing weather and updated forecasts.

A very warm and humid air mass draped across southern Ontario and Quebec is expected to yield strong thunderstorms today. A heat warning is in effect for metro Montreal for Sunday. The combination of very warm temperatures and high humidity, is expected to produce humidex readings (real feel temperatures) close to 40C (104F).  The temperature today will range from 28C (83F) in the Ottawa Valley up to 32C (90F) in metro Montreal.

A strong, slow moving cold front will begin to influence the weather across eastern Ontario this afternoon, and by the supper hour in Montreal. Strong to severe thunderstorms are possible between 5pm and 8pm Sunday in Montreal, with the main threat being strong winds, heavy rain and frequent lightning. There is a risk of hail with the strongest storms, and an isolated tornado can't be ruled out. The storms that did develop in Ontario on Saturday prompted tornado warnings in and around
Toronto. Strong circulation was noted with supercell thunderstorms, along with 64mm of rain in North York.

Showers and thunderstorms will continue into the overnight hours in Montreal, while diminishing in strength. On Monday, the weather will remain warm and muggy, with a continued threat for thunderstorms. The strongest storms however will be to the east of Montreal on Monday, over the Eastern Townships, Beauce and New England. On Monday, heavy rain is possible as well, with the threat for flash flooding across upstate New York and Vermont. Flash flood watches are widespread across those regions. Expect dry and cooler weather to return by Tuesday.