UPDATE, 11:3OAM: A Severe Thunderstorm Watch has been issued for Montreal and Ottawa as well as most of southern Quebec and eastern Ontario through this evening. Conditions are favourable for severe storms to develop in the soupy atmosphere this afternoon. The main threat will be very heavy rainfall, but hail and strong winds are also possible.
UPDATE, 6AM, July 5, 2019: Heat warnings remain in effect today across the entire region. Very warm and humid air remains in place across southern Quebec to end the work week, with another scorcher on tap today. Thursday was the warmest day of the year to date across metro Montreal, with temperatures ranging from 32.5C (91F) at Trudeau Airport up to 35C (95F) downtown. Today, Montreal should reach 32C (90F), which should be enough to break the record for the date set in 2016 of 30.2C (86.2F).
Today and Saturday will be the most humid days of the week, with humidex values approaching 40C. A cold front will begin to generate showers and thunderstorms in the muggy air mass, as early as this afternoon. More storms are likely overnight and into Saturday morning, before the front clears the region and the air begins to cool and dry out. Some of the storms will be severe, with heavy rain and isolated flash flooding the biggest threat. High pressure returns to end the weekend, with near perfect summer weather persisting into the middle of next week. Sunday will be sunny and less humid, with a pleasant high of 25C (77F).
UPDATE, 8:15AM, July 4, 2019: Widespread heat warnings and special weather statements remain in effect from Ontario into Atlantic Canada, including metro Montreal. For Montreal, the story is simple, hot and humid. The current temperature at 8am was already 24C (76F) in Montreal, with a humidex of 30C (86F).
Expect high temperatures through Saturday between 29C and 34C (85 to 95F). Humidity levels will be on the rise, especially Friday and Saturday, with humidex values approaching 40C. A stray shower or thunderstorm can't be ruled out Friday afternoon, but the bulk of the activity here in the Saint Lawrence Valley will be along a cold front Saturday. On Saturday, some of the storms may be severe, with the main threat being very heavy rainfall. Cooler, drier air returns for Sunday, with a high of 24C (76F).
Previous Post: A very warm and humid air mass has prompted heat warnings for metro Montreal as well as the Ottawa Valley and eastern Ontario. High pressure will dominate the weather for the balance of the week, with sunny, hazy and humid days expected, along with very warm nights. High temperatures across the region will range from the middle 30s in urban areas to the low 30s (90-95F) away from the city. Overnight lows are forecast to be near 20C (68F). Humidex values will approach 40C, (104F), especially by Friday when the high is forecast to be 34C (94F) in Montreal. New records however will be hard to come by, as the heat will not be nearly as intense as that observed in July 2018. The only exception could come on Friday, with a forecast high of 34C easily beating out the record for the date of 30.2C set in 2016.
Environment and Climate Change Canada recommends that you protect yourself from the excessive heat by drinking 6 to 8 glasses of water per day, as well as spending several hours in air conditioned or cool places. Try to limit outdoor physical activities, especially during the daylight hours. As always, check on your elderly neighbours, love ones or those living alone. During the July 2018 heatwave, over 65 deaths were reported in Montreal alone. According to Montreal Mayor Valerie Plante, the city is ready this year to extend hours for pools, libraries, community centres and homeless shelters as needed. Workers will also be checking on residents and handing out water bottles to the homeless in an attempt to encourage citizens to stay cool and hydrated. Authorities also remind you the obvious, never leave your child or pet unattended in a hot car. In 30 degree plus weather, injury or even death can occur quickly.
The heat is forecast to ease slightly on Saturday, along with the risk for showers and thunderstorms. This heatwave comes during what has been to date a rather cool year. The first 6 months of 2019 have featured below normal temperatures in Montreal. The average high in June of 18.3C, was 0.3C below normal. The last month to have above normal temperatures in Montreal was back in September 2018. Montreal recorded 21 days over 30C in 2018, but only one day so far in 2019.