Hot and humid weekend ahead for southern Quebec

The St. Lawrence River along the Verdun shoreline taken Monday, July 25. Skies cleared behind a cold front early in the day leaving some fair weather clouds along with strong west winds, gusting up to 73km/h. This was part of what turned out to be a fairly average July in the Montreal. (ValleyWeather Photo)

A soupy airmass has arrived in Montreal as a warm front lifted across the St. Lawrence Valley Thursday morning. Hot and humid air is streaming north into the region. Clouds and scattered showers will likely hold temperatures down in Montreal Thursday, perhaps reaching 28C (83F). Regions south and east of the city are forecasting highs well into the 30s. Factoring in the humidity,  the weather will feel closer to 40C (104F) outdoors. Overnight lows temperatures will remain very warm and sticky through Sunday, between 21C and 23C (70 to 73F).

More showers and isolated thunderstorms are possible through Thursday night and Friday, as a weak front moves across the region. That front will wash out late Friday, allowing the heat and humidity to build back in. Highs Friday will once again be held into the upper 20s, but will rise into the low 30s with elevated humidity both Saturday and Sunday. The weather will be oppressive this weekend,  keep this in mind if you have outdoor activities planned. Drink plenty of fluids and watch for heat stroke.

Late Sunday a more potent cold front will arrive with plenty of showers and isolated thunderstorms. With the moisture latent airmass in place, there is the risk for some very heavy rainfall late Sunday and Monday in the St. Lawrence Valley. Much cooler weather will arrive to start next week, with temperatures falling back into the middle 20s. 

July Summary

July was just ok in Montreal, nothing spectacular. Temperatures were close to normal, with an average high of 27.1C (80.8F) in Montreal. The long-term average is 26.3C (79.3F). Montreal recorded only four 30C days in July, but 6 additional days fell just shy of that, between 29C and 29.9C.

We managed 73.6mm of rain in July, most of that falling during a few hours on the evening of the 18th.  The normal for the month in Montreal is 89.3mm. Most thunderstorms managed to skip around Montreal, preferring a path through the Laurentians. For that reason, the first four tornadoes of the 2022 season in Quebec, occurred over that region. On July 1st an EF-1 tornado occurred at Val-de-Lacs. Winds were estimated at 145km/h. Damage and power outages were reported. A strong line of thunderstorms produced three more tornadoes on July 23 near Saint-Adolphe-d'Howard. The strongest, and EF-2, with winds estimated at 200km/h, caused extensive damage to several homes and knocked out power to thousands. Two other satellite tornadoes, an EF-0 with 110km/h winds and an EF-1 with 140km/h winds spun off from the main storm, uprooting trees and snapping power poles. Thankfully no injuries were reported in any of the storms.

Briefly looking ahead to August, it appears southern Quebec will be warm and humid, with slightly above-normal temperatures. A fierce heatwave that has scorched the southern and central plains will begin to expand north and east allowing some of the warmth to arrive in southern Ontario and Quebec.