Sarnia's winters are cold and variable, with temperatures often dipping below freezing but occasionally warming up to mild highs. As the seasons shift into spring, temperatures gradually rise, with April and May experiencing a significant increase in warmth, with average temperatures reaching above 13°C. Summer months of June, July, and August bring warm to hot conditions, with high temperatures frequently reaching the mid-30s Celsius. Autumn is generally cool, with September being the mildest month before temperatures drop again in November and December, signaling the return of winter's chill.