7PM Update: The severe thunderstorm watch has expired as of 7pm. Most of the thunderstorm activity has remained south of the border across northeast New York and central Vermont. Isolated showers and storms are still possible into the overnight in Montreal, but they should remain below the severe threshold. The month remains rather dry, with only 1mm of rain falling on Ile Perrot today.
Strong thunderstorms will continue to impact the border region, especially across the Eastern Townships and Beauce.
Previous Post: Environment Canada has posted a severe thunderstorm watch for most of southern Quebec including metro Montreal, as well as eastern Ontario. A warm and humid air mass has been over the region since Monday, with scattered thunderstorms developing over the region.
A well defined trough of low pressure will move across northern New England this afternoon. The potential exists for strong thunderstorms to develop over the entire region, but especially from Montreal south into New York and Vermont.
The biggest threat with any storms will be strong winds and torrential rain. Dangerous lightning and small hail are also possible. A watch is issued when conditions are favourable for for strong storms. A warning is issued when the storm is imminent. Anyone with outdoor activities this afternoon should keep a watchful eye on the sky and seek shelter immediately if threatening weather approaches.
So far in August, most of the storms have avoided the Montreal region. Trudeau Airport has recorded no precipitation in August, with the last appreciable rain falling on July 11.