Sarnia, Ontario, will see a drastic change in weather this week as unseasonably warm temperatures on Monday give way to freezing conditions by mid-week. According to Environment Canada, the community will reach a high of 15°C on Monday, March 9, 2026, before the spring-like weather ends abruptly.
The warm spell is expected to fade on Tuesday, March 10, 2026, as the region transitions to cloudy skies and rain showers. By Wednesday night, March 11, 2026, temperatures are projected to drop significantly to a low of -5°C.
Forecasters expect a mix of rain and flurries to continue from Tuesday through Friday, March 13, 2026. These changing conditions could create slushy or icy roads for local drivers as the temperature remains near or below freezing throughout the end of the week.
This shift marks a return to typical March weather for the area near Lake Huron and the St. Clair River, where temperatures usually range between 5°C and -5°C. While the early part of the week offers a brief taste of spring, winter conditions will settle back in for the remainder of the week.
