Strong thunderstorms cooler weather on tap for Montreal

Dense fog early Monday morning across the Montreal region, should burn off leading to a warm and muggy day, with strong thunderstorms expected by late afternoon. (ValleyWeather Photo)

Dense fog to start the day followed by the threat for strong to severe thunderstorms for metro Montreal.

As of 6am, visibility was down to 0.2km at Trudeau Airport in the fog, so drive safely.

Our early taste of summer will come to an end briefly over the next 24 as a strong cold front and upper level low move into southern Quebec later Monday. Sunday was another unseasonably warm and muggy day, with highs reaching 24C (76F) in Montreal. This after three consecutive days of record-breaking  highs in the low 30s. There were numerous scattered thunderstorms and downpours across Ontario and Quebec, but most missed my location here on Ile Perot, with only 1.5mm of rain falling, with 0.4mm at Trudeau Airport.

We have one more muggy, warm and humid day before a change in the airmass occurs. Monday morning dawns misty and foggy for many after the overnight full lunar eclipse, for those who were lucky enough to view the celestial event. We should have a few hours of sunshine after the fog burns off and before the clouds increase around noon. Temperatures should quickly rise into the middle 20s. A broken line of thunderstorms is expected to develop across upstate New York and eastern Ontario and move east into southwestern Quebec by 3pm. Some of the storms may be strong, with heavy rain, hail, frequent lightning and gusty winds the main threat. A severe thunderstorm watch may be needed for a portion of our area.

The weather will become rainy tonight as the upper level low swings into southern Quebec. Winds will increase out of the northwest up to 70km/h and temperatures will turn noticeably cooler, with a low of 12C (54F). The high on Tuesday under showery, blustery conditions, will only be 15C (59F). The upper level low will gradually move northeast out of our region by Wednesday, with clearing skies and moderating temperatures.

We have had a very dry month to date, with only 7.6mm of rain falling in Montreal. That should change over the next 24 hours, with the potential for 25 to 50mm (1-2 inches) of rain between thunderstorms and post-frontal showers.

Be safe today, if you have any outdoor activities planned, be aware of thunderstorm development.