Published on May. 10, 2026, 5:00 PM
Updated on May. 10, 2026, 5:54 PM
A good rule of thumb for planting frost-sensitive plants is to wait until after the May long weekend, and this year is no exception.
A rare, mid-May hard freeze, is coming to a city near you.
A widespread, potentially damaging frost is forecast across a large chunk of southern Ontario this week as we accelerate towards mid-May.
“Damage to plants, trees, and crops is possible,” warns Environment and Climate Change Canada (ECCC) in the frost advisory. “Cover up plants, especially those in frost-prone areas.”
SEE ALSO: The ‘3Cs’ you need to know to protect your plants from frost
The pattern
A textbook recipe for a hard-freeze is imminent, with the pattern beginning to develop on Monday. An unusually chilly, high-pressure system migrates in from the northwest on Monday.
By Monday night, the centre of the high with the lightest winds crosses southern Ontario, allowing ground temperatures to reach lower temperatures.
RELATED: Stuck in a lull: Will pleasant spring weather ever reach Ontario?
Wind speeds are forecast to be approximately 5 km/h in the pre-dawn hours on Tuesday, with even calmer conditions locally likely.
