Winters in Sundsvall are harsh and cold, with temperatures often dropping below -20°C in January and February. Despite this, the coldest months also see some mild days, allowing temperatures to rise above freezing. As winter gives way to spring, temperatures gradually warm up, reaching averages around 1-3°C by March and April. Summers are pleasant, with July being the warmest month, averaging around 18°C, but still experiencing some cool nights. Autumn brings a return to cooler temperatures, with averages in October and November often below freezing, while December sees another cold spell.