Weather in September vs October

Mid to late October is generally not cold, but getting cool in the evenings. However there is a high chance of rain. Whether it will be the case the year you go nobody knows. They haven’t figured out how to forecast weather beyond a week or so ahead.

I was in Rome, Naples and the Tyrrhenian Sea coast in September 2022. It was warm and even hot a good deal of the time. If you go in September, you'll have nothing to worry about regarding warmth to sit outside. Most nights, I was sitting outside for dinner.

I was also in northern Italy and Rome in November 1994. It was mostly temperate. Only on the last day was there a bit of cool in Milan. But as you see above, I'm from Chicago. What's cool to me is cold to others.

Sorry, but I cannot speak about October. However, September and November were no problem.

We have spent the month of September and then a week or so into October three times, and it was too hot for us all three times. We swore "No more September!" after our 2022 trip to the eastern part of Tuscany and to Liguria, but we have sworn off many things and then done them. I should say that we hate being hot more than most people do.

So, here's what may be more helpful to you --- it's been our experience that in the cities you can easily find places to eat with outdoor seating in October, but in smaller towns, no matter how warm and sunny it is, the restaurants seem to move their seating indoors. Maybe because even early October is "fall" and time to move inside no matter what the temperature is, maybe because the tourist crowds die down a bit and then restaurants don't want their customers so inconveniently spread out? Maybe what we experienced was just a coincidence? Because of COVID, I really really wanted outdoor seating or at least a table next to an open window, but in every single town we visited in Liguria in October, outdoor or well-ventilated seating were not available. In the big city of Genoa, though, we ate street food at outdoor tables. So my guess is that you'll be fine in Venice, Florence, Rome, and Naples (where we ate outdoors on a December trip!)

With the climatic change now Italy is incredible warmer. September is still absolutely a sunny month, even if at the end and in October temperature could become lower during the night.
October is usually a rainy month, but now there are so sparse rainy day that it's almost not an issue to take in account. In the last 2/3 years October has been very pleasant: not hot during the day (at least far from 40°C) and little more chilly during the night.
(Pleasant from a touristic point of view: to walk around and enjoy the place. For everything else the lack of rain is nightmare! Enjoy Italy before it become a desert)

We were in Rome & Naples in late Oct first week in Nov this past year. It was warm most days and we only had one slight day of rain while traveling to Orvieto in two weeks.

My daughter studied in Rome this fall semester and said Sept was very hot & very crowded.

If it was me I would go late Oct or early Nov again. Enjoy

TY all for your replies. Climate/weather uncertainty is all part of the experience.