If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Jablonec nad Nisou: The hottest months are usually July and August with an average temp of 61°F, while the coldest months are January and February with an average of 32°F. The snowiest months in Jablonec nad Nisou are December, January, November, and February, with each month seeing an average of 5 inches of snowfall.