High heat and humidity through Sunday for Montreal

High pressure combined with the remains of tropical storm Barry, will deliver a dangerously hot and humid air mass to southern Quebec and the Eastern Seaboard from Friday through Sunday.

Widespread heat warnings have been posted by Environment Canada for the majority of southern and eastern Ontario into southern Quebec through Saturday. The last two weeks of July are traditionally vacation period here in Quebec, so plan your outdoor activities accordingly, taking into account the dangerous heat that is forecast.

South of the border, heat advisories stretch across the Midwest, Great Lakes and Ohio Valley, into New England, the Northeast and south all the way to the Carolinas. The combination of heat and humidity will push temperatures over 100F this weekend.

A warm front will move across southern Quebec Thursday night into Friday morning, accompanied by showers and isolated thunderstorms. On Friday, very warm and moist air will stream into the region on gusty southwest winds up to 50km/h. Skies will become partly cloudy and hazy by noon, with temperatures surging into the low to middle 30s. The forecast high for Montreal on Friday is 33C (92F), with humidex values approaching 40C (104F).

There will be no relief for Montreal Friday night, with lows remaining in the middle 20s. Saturday promises to be one of the warmest days of the year, with highs in the middle 30s and humidex values rising into the low 40s across southern Quebec.

The high humidex values pose a significant risk for heat stress and heat related illnesses. Drink plenty of fluids, seek out air conditioning for at least part of the day, make certain to check on older relatives and neighbours. Be extra vigilant if you work outdoors or have activities planned through Sunday. Never leave pets or children unattended in vehicles in any heat. Car interiors can reach lethal temperatures within minutes.

Relief will arrive during Sunday, with the approach of a vigorous cold front. Strong to severe thunderstorms are expected across the Great Lakes and Saint Lawrence Valley southward into New England. Much cooler and drier air will arrive behind the front, remaining well into next week.