Winters in Oshawa are cold and variable, with temperatures frequently dropping below -20°C in January and February. Spring brings a slow warming trend, with March temperatures often fluctuating between freezing and mild conditions. Summer is warm but not hot, with highs rarely exceeding 32°C, while autumns are similar to springs, with temperatures gradually cooling over the course of the season. Frosts can occur as early as October, and snowfall is common in November and December. The coldest months tend to be from January to March, while the warmest months are June to August.