Winters in Hameenlinna are harsh and cold, with temperatures often dropping below -20°C in January and February, but slowly warming up by March. Spring arrives in April, bringing moderate temperatures around 0-10°C, but May sees a significant rise to average highs of 20°C. Summer is mild and pleasant, with June and July averaging around 20°C, while August cools down slightly. Autumn is crisp and cool, with September and October experiencing temperature fluctuations between 0-15°C, before winter's chill returns in November and December.