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Rare thundersnow reported in southern Ontario

Tuesday, May 12th 2020, 6:48 pm - Thundersnow is a rare type of weather that typically occurs during the winter months.

Reports of thundersnow in Kingston and surrounding regions add to the atypical spring weather that southern Ontario has seen this May.

Snow, graupel and a few rumbles of thunder were reported at the Kingston International Airport shortly after 4:00 p.m. on May 12. The unique atmospheric setup created the right conditions for thundersnow to strike and this wintry precipitation to fall.

coldair (1)

The angle of the Sun caused air parcels to rise several kilometres up into the cold, unstable air aloft where temperatures were around -20°C. Temperatures near the ground were cold enough for the precipitation to fall as snow instead of rain.

“The air aloft was so chilly that super-cooled water droplets accreted on the falling snowflakes before they reached the surface, distorting the classic snowflake,” says Weather Network meteorologist Tyler Hamilton.

It can be tricky for moisture, atmospheric instability, a lifting mechanism and air that is cold at the surface but warmer than the air aloft to all occur at the same time during the winter months. When all of these conditions come together, an electrical charge separation within the cloud builds as the upward motion of air increases snow growth, which results in a lightning strike.


Hamilton says that thundersnow is a rare form of weather that normally occurs during the winter and it’s particularly unusual that it occurred in the middle of May.

"Warm air is expected to flood most of the region next week, which will finally give us the first true taste of early summer weather," Hamilton adds.

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