Italy

September and October.

I like going in May.

Mid April until the end of May, and mid Sept. until the end of Oct.

April-May or mid-September-October are my favorite times.

Agree with September and October but more late September. Early September can still be uncomfortably warm in cities like Rome. April is great for beating crowds as long as you are avoiding the weeks surrounding Easter. We went in April one year and it rained a lot. Short but strong bursts of rain every day. But we were prepared and didn't let it ruin our trip.

My trip last year was mid-October to early November. The weather was quite pleasant, and only had to deal with rain during two days in November in Venice and Milan, plus a bit of drizzle one morning in October in Sorrento that was barely worth noting.

I've also travelled in Italy late May. Also had some rain to deal with during this trip, including a downpour in Venice during a gondola ride, and one day in Rome. I dont think I've ever been so wet in my life than after that gondola ride! My shoes took 3 days to dry.

Foul weather can happen any time of the year so be prepared with a light rain jacket and an extra pair of shoes. Umbrella sellers pop outta the woodwork any time the weather turns bad, and the prices are reasonable. I would say that for fewer crowds that late October was much better than May, with November even better (plus the hotel prices drop in November).

TC said it perfectly, IMHO. Of course just where in Italy makes a significant difference. Sicily to the Dolomites is a long way, south to north.

We just returned from Paris, Switzerland & Italy--we were there from February 25-March 14. From a 'crowd relief' standpoint, it was fantastic, except on the weekends, when places like Musee D'Orsay in Paris and the areas near the Uffizi and Il Duomo in Florence were very busy, more than I like for sure.

It was the not-unexpected weather that took a little getting used to, however. Paris averaged about 40-45 F, but dang, it seemed colder than 20 in Chicago. Biting wind. Not all the time, however. When the wind died down, it was fine. Lucerne, Switzerland, even at 40 degrees was great because it was sunny and the sun just seemed warmer at that altitude. Florence (we got there March 4) was windy, with a little rain. But on those days when the sun came out, it was like immediate spring, even though the temps were still no higher than the low 50's. Then in Salerno, south of Naples, it pretty much was spring, 50's for the most part, and we even got up to 60 while on the Amalfi Coast and at Pompei. Absolutely glorious weather. Still chilly at night, though, down near 40.

I did prepare clothing-wise, though. I can't stand being too hot, so most of the time, I utilized one of those ultra-light down jackets (mine was made by Marmot) that when traveling compresses down into a ball the size of a toiletries case--I wore a fleece on the trains. Even when it was cold, that down jacket over a golf shirt was all I needed. Never wore the gloves I brought, but did wear my knit hat quite often to keep my ears warm.

I will also say that we took trains all the way from Paris-->Lucerne-->Milan-->Florence-->Salerno, and never once was our train filled to capacity. Granted, on the non-regional lines we had reservations, but we really enjoyed having extra space for our bags, and to stretch out. Made traveling by rail an absolute pleasure. Don't know how that would be in the high season, however.

Bottom line? I will take cold over too many tourists any day of the week. If I were doing it again (and probably will at some point), I think about 3-4 weeks later than we traveled, right around the 1st of April, would be optimum, even for northern Italy. You may pay a tad more for hotel & air, but will still have the run of the places for the most part. Weekends will still be busy. Can't get around that, and with the Euro & dollar pretty much even, there definitely will be more folks traveling to Europe until that status changes.

See also http://www.ricksteves.com/travel-tips/trip-planning/timing-your-trip.

We usually hit Italy from mid-Sept to beginning Oct. Last year, we went the first week of Sept. Rome and Amalfi coast was really hot - as in, having to retreat to the room for a few hours in the afternoon and most days taking 2 showers. Weather was much more tolerable when we hit Venice mid-Sept, it was much more tolerable. I do realize Venice if farther North...but add another vote for mid-Sept to early Oct! Guess it depends on your tolerance to heat.