Planning for the weather is a good way to make your trip to Siuntio relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August, with an average temperature of 16°C, while the coldest months are January and February, with an average of -2°C. The snowiest months in Siuntio are January, March, December and November, with each month seeing an average of 28 cm of snowfall.