Do I need airconditioning in Venice in mid-June?

Tina, it really depends. I've been in Venice in early June and it was fine, and other years at the same time it was hot and humid at night. Check with your hotel to see if they have fans in the room, or if one can be available if needed (I had a fan in a non-air-conditioned room in Florence in late July and it was sufficient).

The mosquitos will eat you alive if you sleep with your window open in June. Get a hotel with AC!

Thank you! That really helps a lot.

I agree with Tim about the mosquitoes. Unless you are a light sleeper I would not plan on keeping windows open in the big cities, there is too much noise. Even the "newer" buildings are quite old and not fitted in insulation that we are accustomed to in North America.

It's quite likely that you will wish for AC if you don't have it. I was there in September and it was very hot.

I always get a/c for summer months in Venice.
Humidity and insect bites at night do not make a gd vacation

We left Venice two days ago and it was warm already. We had to keep the windows open in our apartment because the A/C is not available until June 1st, and we had plenty of mosquitos as a result. We were in Venice in May last year and it was really hot. Do not consider a place without A/C!

Go to this Weather Underground link to see the historical trend for Venice in mid-June. note that the nighttime lows often don't get below the upper 60s. Throw in massive humidity and you're going to want AC, imho. Happy travels.