Air conditioning in hotels

All of the hotels I've used in those cities have had air conditioning. However, some of them may not switch it on until the really hot weather appears. The websites of hotels you're considering you have information on A/C, or check the Guidebooks.

Glancing at the Florence listings, for instance, in Rick's Italy book, they specifically say "air-con," in the places where you can expect it, which is most of them.

Even when there is "AC" in Italy hotels, it often won't be the kind you're used to in the US, where you just push the button and you get a blast of cold air for as long as you want that is capable of refrigerating the room if you desire. Electricity is expensive in Italy and the room AC is often configured by the hotel in a way that makes it somewhat more limited than here. But in the summer, any AC in Rome and Florence will be better than none.

All the hotels I've visited so far in Italy had AC. (Usually charged an additional 5 euro or so a night.) The AC's are often not turned on when you get the room so expect it to take a while for things to cool off. All the hotels we stayed in provided a remote that controlled the AC unit so we could adjust it to our comfort level.

I have had AC in all the hotels that I have stayed in. I have to say that it would be impossible at any of them to get the room really cold. My husband complained to me but I was comfortable!

In California I pay approx $0.12 per kWh.
The rate in Italy is €0.484 per kWh for homes (that is what I pay in mine where my mom lives) and even more for businesses.
So the rate for electricity in Italy is at least five times what we pay in the US (even more for businesses). So don't expect hotels to keep the a/c on when nobody is in the room.

Adding to Kent's comment about A/C not being what you (might) be used to, many places have a horizontal contraption mounted over a doorway, or up high against the wall where it meets the ceiling, and that's your A/C box. There will probably be a remote control device, similar to what's used for TV's, for operating it. Just make sure you set it to cool, not heat the room (found out the hard way, once).

Who needs AC in Venice when you can avail yourself to an Aperol Spritz to cool down after a day of walking about. The Italians have no problem with a little ice in the drink.