If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Busto Arsizio: The hottest months are usually July and August with an average temp of 71°F, while the coldest months are January and December with an average of 41°F. The rainiest months in Busto Arsizio are November, October, May, and August, with each month seeing an average of 8 inches of rainfall.