Elevated heat and thunderstorms for southern Ontario and Quebec

Temperatures are forecasting to soar into the middle 30s across many locations in Ontario and Quebec on Wednesday. If you have outdoor plans on this Canada Day, do so carefully.

Happy Canada Day! Stay cool, stay hydrated.

Heat warning in effect for eastern Ontario and southern Quebec, including metro Montreal.

The heat is on! Numerous forms of weather warnings and advisories are in place for extreme heat, impacting millions of residents across the eastern United States and Canada, as high heat and humidity levels prevail. If that were not enough, we are contending with strong to severe thunderstorms as well.

Starting with the forecast, we are already warm Wednesday morning in Montreal, despite persistent cloud cover and even a few showers around. Temperatures are already in the middle 20s, with humidex values over 30C. Wednesday will be warm and humid, with a high near 33C (92F). There is a risk of strong thunderstorms late in the day. Overnight will remain very warm and muggy, with temperatures around 25C (77F). Thursday will be a repeat of today.

As far as thunderstorms are concerned, the risk remains high, but the exact location of the storms is not so clear. On Tuesday, several strong clusters of storms moved around the edge of the high pressure producing all this heat, sliding southeast across Ontario, between Cornwall and Kingston. The storms occurred in waves, prompting tornado warnings and resulting in damage. Widespread power outages occurred along with significant tree damage and flooding. Winds gusted in excess of 100km/h at sveral locations, and there were thousands of lightning strikes.

Similar storms are possible later Wednesday and again Thursday afternoon, stay alert if you have outdoor plans, especially across our western locations towards the Ontario border.

Wednesday will be hot. Some locations in Ontario and upstate New York, less likely in Québec, may flirt with the 100F mark Wednesday. On Tuesday, Windsor, Ontario reached 35C (95F), they are forecasting 37C (98.6F) on Wednesday. 

Montreal's warmest temperature occurred on August 1, 1975, when Trudeau Airport reached 37.6C (99F). Unofficially several downtown locations exceeded the 100F mark during the 1975 heatwave, however officially, the city has never hit the century mark. That record has come close to falling, but still stands after 51 years, and should remain safe this week.

Montreal heatwave to last through Saturday

Elevated heat and humidity is expected in Montreal through at least Saturday. Daytime high temperatures will range from 32C to 34C (90 to 95F), with humidex values well over 40C (104F).

A yellow weather warning for extreme heat is in effect for metro Montreal.

In fact, heat warnings and advisories of some form stretch across southern Ontario, southwestern Quebec and a large portion the Untied States, east of the Mississippi River.

Strong high pressure over the southern US is pushing a very warm and moist air mass into our region. Temperatures will rise into the low and middle 30s for some locations, with elevated humidity levels, especially Wednesday and Thursday resulting in humidex (real feel) temperatures over 40C (104F).

The reminders are the same with this kind of heat, drink plenty of water, refrain form strenuous outdoor activities, especially during the afternoon hours. Try to spend some time in air conditioned spaces if possible. The most simple advice is often the most difficult for some to follow, under no circumstances, none, do you leave pets or children unattended in vehicles.

Extreme heat can be a killer. Watch for heat exhaustion and heat stroke. Know the difference and most importantly know how to respond. Always stay hydrated. (NWS)

If you have plans to move on July 1st, as many do in Montreal, plan for very uncomfortable and at times dangerous conditions. Drink plenty of water, avoid alcohol, pizza is ok :) and take frequent breaks.

Little relief is expected overnight, with temperatures remaining very warm in Montreal, in the middle 20s (70s F). The cumulative effect of a few days of extreme heat is often what leads to health issues.

There is a chance of some strong thunderstorms late each day as disturbances in the atmosphere ride along the northern edge of the high pressure ridge. The first risk arrives Tuesday afternoon. Some of the storms may be severe, with high wind gusts and torrential rainfall.

Relief may arrive by Saturday as a cold front moves southeast from western Canada. The timing is not clear at the moment, but temperatures should cool slightly by Sunday.

Heat, humidity and thunderstorms - July in Montreal

The calm after the storm as a vibrant rainbow graces the Montreal skyline. The weather has been very active and highly changeable this month in Montreal. (Photo Norman Leblanc)

A dome of high pressure is forecast to strengthen across the midwestern United States this weekend and into next week, providing a large portion of eastern North America with increasing heat and humidity. The warmest temperatures, approaching 38C (100F) in some locations, will be found across the Ohio Valley, Midwest and Middle Atlantic states.

Montreal, southwestern Quebec and eastern Ontario will be on the northeast edge of the heat dome, with warm and humid weather and occasional thunderstorms starting Monday. We call those systems that produce then thunderstorms ridge runners or ridge rollers, disturbances the move along the periphery of the nearly stationary ridge of high pressure.

Typically these can produce strong, very moist thunderstorms, just what Montreal does not need. The best chance for those storms would be next Wednesday and Thursday, however isolated cells can pop up anytime in the warm and humid airmass.

June in Montreal can be summarized in this one photo, as thunderstorms and sunshine have battled all month. The result has been highly changeable weather along with plenty of rainy weekends. (Valley Weather Photo)

Before that, we have a cold front arriving Friday, with scattered showers and thunderstorms. It does not look like a repeat of last Saturday, with most storms rapidly moving from west to east across the region. My experience in Montreal in both the recent flash flooding event all the way back to the infamous 1987 Decarie Expressway flood, is that it is the north to south or south to north moving storms are the ones that cause us the most trouble.

It has been a wet June, already closing in on 150mm (6 inches) of rain at Trudeau Airport, with some locations in the city easily surpassing 250mm (10 inches), so anymore rain will only add the saturated ground and full rivers and lakes.

As far as temperatures are concerned, we will reach 22C (72F)  Friday, before the heat starts to build through the weekend and into next week. High temperatures will rise into the upper 20s and low 30s by the middle of next week. High humidity will push humidex values into the upper 30s to near 40C across large parts of southern Quebec and eastern Ontario.

Devastating flash flooding on the West Island

Heavy rain from strong thunderstorms quickly overwhelmed the sewer system, inundating roads across parts of the West Island on Saturday afternoon. (West Island Community Page via Facebook)

Powerful moisture-latent thunderstorms swept across parts of the West Island and South Shore on Saturday afternoon, producing nearly two month's worth of rainfall in just a few hours. The slow moving thunderstorms impacted a relatively small area of the Island of Montreal, focusing on Pierrefonds-Roxboro, Pointe-Claire and Dollard-Des Ormeaux. In those communities as much as 170mm of rain fell between 3 pm and 7 pm.

Heavy rain also fell in Dorval, with 60mm at Trudeau Airport. In stark contrast, I only measured 5mm at my weather station here on Ile Perrot.

The result of the torrential rain was immediate, with several main roads, including Highway 40 between Sources and Saint John's Boulevard becoming inundated with water and impassable. Drivers became trapped in their cars by rising flood waters, with at least 15 requiring rescue by Montreal Firefighters. Montreal Division Fire Chief, Martin Guilbault, said his department responded to nearly 800 calls within the first hour of flooding and close to 1200 overall.

At least a dozen communities have been impacted by devastating flooding, affecting hundreds of homes and vehicles.

The Montreal Fire Department responded to over 800 calls in  first hour after the flooding began. Above the department arrives to rescue drivers trapped in their vehicles on Gouin Boulevard in Pierrefonds. (Photo Peter Turnbal)

Nearly four hours of lightning at Trudeau Airport, resulted in a ground stop for safety reasons. Dozens of flights were canceled or delayed and at least 25 incoming flights were diverted to other airports. Between 3 pm and 7 pm it was a constant rumble of thunder to my east over the West Island as dark clouds moved from northwest to southeast and onto the South Shore.

Hail and strong wind gusts also occurred with the storms. As a result of the flooding, Hydro-Quebec needed to cut power to most of the affected area. That combined with other storm effects, such as wind and lightning, resulted in the loss of power to over 25,000 customers. Most of the power was restored early Sunday according to  media relations spokesperson Paule Veilleux-Turcotte.

At least 300 homes were severely damaged by flood waters, but that number is likely much higher. The clean up began in earnest on Sunday, but was interrupted by more weather warnings and thunderstorms. Sunday's storms were a little more tame, as the Atlantic Canada system began to weaken. They still managed to dump heavy rain over the area, with 16.2mm on Ile Perrot in just 30 minutes. That storm also produced hail and strong wind gusts.

As Saturday's storms moved onto the South Shore, more significant flooding and road closures occurred in Saint-Constant, La Prairie, Chateauguay and even as far south as Napierreville.

The thunderstorms were the result of deep moisture pinwheeling around low pressure located over Atlantic Canada. It was the same storm the brought heavy rain and severe weather to Ontario and Quebec last Thursday.

Strong thunderstorms produce flash flooding in parts of Montreal and South Shore

Flash flooding in Pierrefonds on Saturday afternoon. Strong thunderstorms have been moving over the same area for several hours now producing torrential rain, in some cases in excess of 100mm from Laval southeast across Montreal and onto the South Shore. (Photo: Luka Korda via West Island Community Page)

Severe Thunderstorm watches and warnings for southwestern Quebec including metro Montreal through this evening.

Strong thunderstorms have been moving southeast across portions of Laval, through Pierrefonds, Dorval and central portions of the Island of Montreal and onto the South Shore Saturday afternoon, producing widespread lightning and torrential rainfall. Radar estimates and reports form local weather stations are indicating anywhere from 30mm to as much as 100mm has fallen in the last several hours.

At Trudeau Airport, 32.1mm has fallen in the last few hours, with nothing at my weather station on Ile Perrot.

The storms are training over the same region. Flooding has been reported in Pierrefonds and well as on the South Shore in La Prairie and Saint Constant. Several roads have been inundated, while others have significant water accumulations.

Radar is showing more storms developing over the lower Laurentians moving into the Montreal region. Remain vigilant this evening especially after dark. Do not attempt to cross flooded roadways.

Hydro-Quebec is reporting outages to just over 9000 customers at 5:40PM

The showers and storms should weaken after sunset, but more are expected on Sunday. The culprit is strong low pressure over Atlantic Canada sending disturbances in the atmosphere pinwheeling into our region. Conditions should improve Sunday night. 

Radar shows a plume of thunderstorms extending from Laval onto the South Shore. They have been dumping torrential rainfall over the same sections of the city, with 30mm to as much as 100mm falling just in the last few hours.

Another unsettled weather weekend for southern Quebec

The weather has been very active over the last few days in Montreal, with plenty of gusty winds, showers and thunderstorms. Sadly this trend will persist into the upcoming weekend. The tree above tumbled across a Pierrefonds road during Wednesday afternoons storm that hit the West Island. That storm also cut power to more than 60,000 Hydro-Quebec customers. (Photo: Jessica Wasserscheid)

That big low pressure system spinning its way slowly down the St. Lawrence Valley early Friday morning, will continue to influence our weather through the upcoming weekend. Unfortunately that means another weekend where we will be dodging frequent showers and thunderstorms.

The system is strong for June, producing very low barometric pressure readings in southern Quebec, strong wind gusts and plenty of rain and thunderstorms. Fortunately for Montreal, the strongest thunderstorms remained over eastern Ontario, southward into Upstate New York and New England. On Thursday, several tornado watches and warnings were issued in Eastern Ontario as well as Vermont. At least one potential tornado occurred near Woodstock, Vermont and there was rotation observed near Alexandria, Ontario. In the Vermont storm, extensive damage and power outages occurred. Vermont power outages reached over 20,000 Thursday afternoon.

In southern Quebec, winds gusted a high as 70km/h, slowing recovery efforts from Wednesday's storms. Power remains out to just over 5500 Hydro-Quebec customers Friday morning.

In Montreal, it was rain and plenty of it. Another 30-60mm fell across the region. I measured a storm total of 33.2mm on Ile Perrot, bringing my monthly total to 105mm. Trudeau Airport sits at 85.4mm for the month. So if you thought it was a wet June, you would be correct.

Friday will be breezy in Montreal once again, up to 50km/h from the west, along with a few breaks in the clouds. A few disturbances will rotating around the main storm located over the Gulf of St. Lawrence, producing scattered showers and afternoon thunderstorms through at least Sunday. High temperatures will remain cooler for late June, near 20C (68F), perhaps warming into the middle 20s Sunday. Overnight lows will be in the middle teens. 

Another 10-20mm of rain may fall over the next 48 hours, perhaps more in thunderstorms. No severe weather is expected for our region, but gusty winds may accompany any showers or storms.

Airport delays - power outages caused by storms - more expected Thursday

Hail covers the ground in Saint-Louis-de-Gonzague southwest of Montreal during strong thunderstorms Wednesday afternoon. More storms are expected on Thursday. (Photo: Amy Reynolds via Facebook)

A round of strong thunderstorms Wednesday afternoon impacted the extreme southwestern corner of the province, including the West Island portion of Montreal as well as Ile Perrot. The intense cells moved northeast from the New York state border region, later weakening over Laval by late afternoon.

The storms resulted in the loss of power to more than 60,000 Hydro-Quebec customers at the height of the outage. That number was down to 80 breaks Thursday morning, totaling just over 11,000 customers. Most of the damage to the power grid was caused by lighting strikes. Power was also out at Trudeau Airport and most of Dorval, resulting in major flight delays during the late afternoon hours.

The storms also produced significant hail across the region from Ile Perot southwest towards Valleyfield.

On Thursday morning, strong low pressure is lifting across the Great Lakes early, forecast to move north of Montreal to lie near the Gulf of Saint Lawrence on Friday. A warm front will produce heavy rain Thursday morning, followed by a break in the early afternoon. It will be a muggy day, with temperatures in the low 20s.

The trailing cold front will produce strong thunderstorms late afternoon in Montreal, with the risk of  gusty winds up to 90km/h, more hail, lightning and torrential downpours. The unusually strong June low pressure will also generate brisk winds outside of thunderstorm activity, gusting up to 70km/h into the evening hours and 50km/h on Friday. 

Wind warnings are in effect across a large portion of upstate New York and New England and may be extended into southern Quebec. Heavy rain with the storm has prompted warnings north and east of Montreal for up to 80mm of rain. Montreal can expect storm totals of 25-50mm. As of 8AM, 13mm had fallen here on Ile Perrot.

Strong winds both today and Friday may result in isolated tree damage and scattered power outages across the province.