High pressure will slide east of the province on Monday, allowing a southerly flow and sunshine to push temperatures back above freezing. Monday will become sunny with a south wind that will help push afternoon temperatures up to +5°C.
Tuesday will be overcast with light rain in the late afternoon and evening as daytime highs reach +4°C.
A Colorado Low will move into Southern Ontario on Wednesday, and the northern edge of that storm is likely to bring periods of heavy rain and temperatures near +4°C on Wednesday morning. Melting snow and rainfall can cause localized flooding. Rain will change to snow in the afternoon as temperatures drop, and a flash freeze will arrive in the evening.
Daytime highs will fall back below freezing on Thursday and Friday under mostly cloudy skies.