The weather varies in different areas. In the north, it may rain. Their probability decreases as you move to the south. The day can be hot, and by the night can be cool. Umbrella and sweater must be taken.

Depending on the region, usually at the end of May it's already hot and the evenings are warm, but I think it's worth taking a light jacket.

And the current forecast for the coming days at popular resorts can be found on the page "Weather in Italy."

Take the windbreaker and jeans. And then, more "just in case." There already full summer.