italy in october

Should be pleasant. I would take a sweater and lightweight rain jacket (layers). Evenings will most likely get cool, but expect some warm sunny days. October tends to be lovely in Tuscany and Rome.

If you want actual temperature and rainfall data, the Weather Underground website gives the historical info for various locations such as Florence and Rome. For example, see https://www.wunderground.com/history/monthly/iy/guidonia/LIRG/date/2016-10

We spent 2 weeks in Italy last year---late Oct-Nov 3rd. Weather was beautiful----a couple of cloudy days but we never had any rain even thought we were ready for it. Yes, light jackets and sweaters.

Generally pleasant temperatures during the day (high 60s, low 70s F), but a bit cool (low 50s F) at night and early morning.
The very end of October is statistically the rainiest period of the year.
Having said that, you should check the forecast just before you go. Statistics are just averages and may not necessarily reflect what is going to happen this year when you go.

We were in Venice last October and even though it is in the North it was pretty warm the entire time. I mostly wore the short sleeved shirt that I had packed at the last minute, since the longer sleeved shirts were too warm. We also were in Florence this August and it was unusually warm, so that trend might continue. I would take some kind of long sleeved covering, but also several short sleeved items for October.