When you’re planning your getaway to Jämijärvi, be sure to take into account the year-round temperatures. The hottest months are usually July and August with an average temp of 58°F, while the coldest months are January and February with an average of 25°F. The snowiest months in Jämijärvi are December, November, February, and January, with each month seeing an average of 29 inches of snowfall.