Much cooler air arrives in southern Quebec

Our heatwave came to an abrupt end on Monday, with fall-like temperatures observed. Above, a brief heavy rain shower moves through Montreal on Monday morning. While close to 25mm fell at Trudeau Airport, it was far less than many locations north of the city. Between 40 and 90mm fell across the Laurentians towards Quebec City, with Ottawa receiving 105.5mm since late Sunday afternoon.

We had a taste of September weather on Monday after three scorching hot days. The high on Monday in Montreal was only 18.6C (66F) behind a very slow moving cold front. That front was the focus for very heavy rainfall, that oddly enough seemed to skip metro Montreal once again. 

I measured 20.4mm on Ile Perrot, most of that falling overnight into Tuesday morning. Meanwhile, 24.6mm fell at Trudeau Airport since late Sunday, 31.5mm at St. Anicet, 60mm at Rawdon, 90mm at Trois-Rivieres, and an incredible 105.5mm, over 4 inches of rainfall, at Macdonald-Cartier Airport in Ottawa. 

There was very little thunderstorm activity in and around Montreal, allowing for less rainfall. Temperatures and humidity levels were very high over the weekend, with a high of 32.2C (90F) on Saturday, and 32.5C (90.5F) on Sunday. The dewpoint temperature reached a sweltering 23.8C Sunday afternoon, producing a record setting humidex of 43C (109F) in Montreal. All that went away quickly on Monday as much cooler air arrived on chilly northeast winds. 

The slow moving nature of the cold front meant you did not have to go far away from Montreal to find the heat on Monday. Places like Burlington, Vermont, Plattsburgh, NY and Brockville, Ontario still were in the high 20s to near 30C with high humidity.

We have lingering showers and drizzle early Tuesday morning, along with chilly temperatures. Skies should gradually clear in the afternoon, with high temperatures rising into the low 20s. Most of the balance of the week into the weekend looks fair and seasonable, with highs in the middle 20s and lows in the middle teens. The only exception will be the arrival of a cold front Thursday, accompanied by scattered showers and perhaps a rumble of thunder. It will become less humid behind that front, with a refreshing weekend in store, ideal for any outdoor activities.