When you board your flight, wear all the clothes that dress you appropriately for the October weather where you live. That way at least some of the layers will be on you and not in your carry-on bag. And those cabins can be cold anyway.
A jacket with hood or nice parka with hood may be helpful. October rains more than September, and may be cool morning and evenings, but can still be quite hot and sunny midday. I say this from recently lodging the whole month of October in the mountains 70 miles SE of Rome along the coastline. I'm thinking the inland valleys may be warm/hot and sunny as well.
I spent the last two Novembers in Le Marche on the Adriatic, and this year packed a nice heavy pair of jeans, but ended up wearing my cooler cotton summer pants more often.
At times I have packed the RS umbrella and the RS rain cape with hood, both are lightweight, nice useful items, but other times I just wing it.