Frost possible in Ottawa as fall begins

A frost advisory was issued for the GTA on May 11, 2026. Photo: iStock/Getty Images. tbgrant tbgrant

By Natasha O'Neill

Posted Sep 21, 2026 02:55:39 PM.

It seems as if Mother Nature is ushering in autumn across Ottawa with a possible frost risk overnight Tuesday.

Environment Canada is saying that conditions are favourable for frost development overnight as temperatures drop quickly into the evening. Patchy frost is likely for Wednesday morning.

The weather agency is asking people to move cold-sensitive plants, trees and crops inside if possible. Frost can damage some plants.

Temperatures peak Tuesday afternoon at 19 C, and are expected to hover near 5 C overnight.

Sept. 23 is expected to have a 17 C high, and dramatically drop again into the overnight hours.

The forecast shows no rain in the forecast and clear, sunny days with cool overnight lows for the week.

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