Planning for the weather is a good way to make your trip to Colleretto Giacosa relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August with an average temp of 57°F, while the coldest months are January and February with an average of 28°F. The rainiest months in Colleretto Giacosa are November, May, June, and April, with each month seeing an average of 7 inches of rainfall.