Winters in Saint-Hyacinthe are harsh, with temperatures often dropping below -20°C and averaging around -5°C in January. Spring brings a slow warming trend, with April typically seeing temperatures rise above freezing, averaging 8°C. Summer is mild, with July and August being the warmest months, though highs rarely exceed 30°C. Autumn is characterized by a gradual cooling of temperatures, with September experiencing some warmer days before dropping to around 3°C in November. Overall, temperature fluctuations throughout the year are moderate, with average temperatures ranging from -6°C in February to 23°C in August.