Unsettled, humid weather to persist into next week for Montreal

A towering thunderstorm developing in the tropical airmass across the West Island of Montreal during Thursday afternoon. (ValleyWeather Photo)

A heat warning remains in effect for metro Montreal through Saturday. The combination of warm temperatures and high humidity will make it rather uncomfortable for outdoor activities.

A weak cold front is in the process of moving across southern Quebec early Friday afternoon. The front is expected to produce some widely scattered showers and thunderstorms, with the bulk of the activity occurring south and east of the city. The front will wash out over the next 24 hours, leaving us in the same warm and humid airmass well into next week.

Several rounds of showers and possible thunderstorms are forecast right through Tuesday. Most of the time the weather will be dry, but when the storms do occur, they have the potential to produce torrential rain locally, with the risk for flooding.

A flood watch is in effect for northeast New York and Vermont Friday, where flooding has already occurred this week. Conditions have been fairly dry in the Montreal region, with only a few millimetres falling at my home on Ile Perrot this week. Other parts of southern Quebec, New York and New England have reported much higher amounts, mainly in areas that have received persistent thunderstorm activity.

Thursday was suffocating, with a high of 32.5C (90F) in Montreal, with humidex readings close to 40C. Montreal was actually one of the "cooler" locations, with many spots reaching into the middle 30s. The temperature remained warm overnight in the low to middle 20s. The heat prompted a record consumption of power across Quebec. During the afternoon hours, at the peak of daytime heating, a high tension line from Laval to the West Island of Montreal failed, plunging over 200,000 Hydro-Quebec customers into the dark and without air conditioning on one of the warmest days of the year. Traffic lights were out and some intersections became chaotic during the afternoon commute. Most of the power was restored by 5pm. 

Temperatures this weekend will be slightly cooler, in the upper 20s as a result of abundant cloud cover, but the muggy weather will persist.