If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Janske Lazne: 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 29°F. The snowiest months in Janske Lazne are December, November, January, and February, with each month seeing an average of 6 inches of snowfall.