Tuscany in December

Great plan to commemorate 50 years! Congratulations!

I would bring warmer clothes. You can always take off a layer, but if you don't have a warm enough coat, you could be miserable. We are usually wearing winter jackets by then...puffy ones are very common. Bring an umbrella, too, and gloves, scarves, hats, Gortex shoes.

I do not know from personal experience how crowds will be. Christmas gets busy everywhere. I can tell you that in January, Firenze was dead quiet and we had our run of the place!

You should always reserve tickets for Uffizi. Crowds won't be huge but still you may not want to wait in line.

Light sweater and unlined jacket? You are overestimating temperatures. Florence is not Moscow, but winter is winter.

Thanks for the replies! That's just what I was looking for. We'll rethink our wardrobe, although I have been known to drive my Miata to work with the top down when it was 22 degrees!
We plan to hit Florence on Tuesday or Thursday, which are supposed to be less busy days. We've budgeted two days for Florence, but that can be adjusted up or down. We are trying to divide our time between the "must see" attractions and areas more off the beaten path to get a better feel for the community. Our favorite times in Scotland were exploring little known, out of the way Iron Age forts and sitting around the Aga at a small B&B, helping the owner make crab salad out of freshly caught crabs.

Different people have varying degrees of toleration to cold temperatures.
I saw once two Russian guys at a restaurant in Salt Lake with shorts and tan tops while outside was snowing.

Temperatures in Florence in mid December are on average around 50 F during the day. They can easily drop to the low/mid 30's at night.

It's not the rainiest time of the year (end Oct/early Nov is), but if it rains, temperatures won't go down as much at night.

In the hills nearby, it might be a bit chillier, especially at higher altitudes. Also cities tend to be warmer than the countryside due to the presence of buildings.

It may not be a bad idea to pack a lined rain jacket, where you can remove the inside if warmer. You won't likely need very heavy coats however.

Congratulations on your kiss anniversary. 1966 has a special significance for us Florentines (at least those like me who were born already). I will never forget the 4th of November of 1966.

Roberto, we were in Florence August 10-11, 1966 on a People to People tour. There were 64 high school students from Georgia and Alabama. Deb was all of 14 and I was 15. I have a slide of the Doors of Paradise that I took while there. I'm actually going to scan in slides I took in Tuscany and try to replicate them 50 years later.

We were heartbroken when we heard the news of the November flood and the damage it caused.