If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Arbon: The hottest months are usually July and August with an average temp of 62°F, while the coldest months are January and February with an average of 34°F. The rainiest months in Arbon are August, June, July, and May, with each month seeing an average of 7 inches of rainfall.