Sicily trip

I made the mistake of going in the summer; you're a lot smarter than I am! You can see actual, historical, day-by-day weather data on the very useful website timeanddate.com. Check at least the most recent three years; five would be better. I've given you a link to Palermo's data for September 2021, but you should find info for other cities like Siracusa and Catania as well. (I don't know that there is enough difference to worry about.)

For monthly precipitation averages go to Wikipedia's entries for the major cities you plan to visit and look for the colorful Climate chart.

I suspect you'll find September temperatures can still be quite hot in Sicily, but October can be quite a bit wetter, so it's a trade-off.

We were in Sicily late Sept & early Oct. I remember it being very hot & humid. All our places had air conditioning, which made sleeping at night bearable. In every city we visited, there were city parks, which offered shade from trees, park benches for a place to relax and rest. The local people were VERY friendly & welcoming, many acts of kindness. Drink lot's of water. Hope you love it as much as we did!!

On You Tube, a couple "The Global Expats" just spent time in Sicily & have posted over 20 videos in different cities there. If interested, check them out. They focus on regional food & history.

In 2018 we too were there in late September and early October. There were warm days but not overly hot. The evenings and mornings we were in Agrigento we wore light jackets eating outdoors. We had two days with rain and there fog during the evening when in Erice. (The link is to our trip photos.)

We chose to visit Sicily in October to avoid the heat and it worked well. We actually have visited Sicily twice in October. Pleasant days, some warm but not hot.