We were in Italy last October in Bologna, Tuscany and Verona and it was low 80s and high 70s for several weeks. Well into October it finally it dropped from high-70s to low 60s over two days along with some rain. It warmed up a bit back to low 70s as time went on but the switch between estate weather and autunno weather had happened and the heat was not coming back.
I have no idea what was going on in southern Italy except that the Italians were saying that the people who had booked "shoulder" Amalfi and Sicily packages were looking very smart. Check the weather as you get close and decide what this year is going to be like since the weather is clearly getting less dependable and adjust accordingly. Be prepared for the possibility of rain and be aware you may have a transition in the temperatures while you're there since October is a transition month.
As a side note all the shop windows - at least Tuscany and north - had winter jackets, wool hats and scarves which looked ridiculous when it was 78 and seemed suddenly appropriate a few days later.
Have a great trip!
=Tod