If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in New Ulm: The hottest months are usually July and August with an average temp of 69°F, while the coldest months are January and February with an average of 22°F. The snowiest months in New Ulm are March, January, February, and October, with each month seeing an average of 5 inches of snowfall.