Snorkeling is tough after october as the water gets cooler and approaches the air temps which makes it feel even worse.

If you take one of the boats which go out to the reef or into the Sanctuary, Danger Charters provides shorty wetsuits as part of the cost and pretty much all of he other trips will rents wet suits for (IIRC) $10.00. But I still got cold wearing one snorkeling in November.

IMO the closest thing to the Casa, but at a much better location and less expensive, is the Pier House, 1 Duval Street. www.pierhouse.com

Pjk

Thank you Peter!! That was very helpful. I will check out the Pier House!

Weather is a gamble in late December. Could be 80. Could be 60. Beach, pool, and snorkeling weather is not a sure thing. But also consider, in the eastern half of the country, it will be the best anywhere.

Holiday week begins peak season. Don't expect bargains. I agree with Peter, Pier House is an excellent place to stay.

So true! Thank you!

We were there for New Year's two years ago. I wore a sweater and capri pants every evening, and it was far too cold to swim, either in the pool or the ocean. However, it was heaven for biking around during the day.

Too cold to sun bathe by the pool?

It was a little chilly to sunbathe by the pool, but we did have a nice catnap on the sundeck of our guesthouse (Heron House), which was delightful. It was still fabulous for being out and about during the day (biking all around Old Town is one of our favorite things - but it usually involves biking from bar to bar...), but a little chillier than I had anticipated at night (hence the sweater). It was the first time that we were in KW in winter - usually we are there no earlier than late April for the Conch Republic Days Festival. But remember that winter in the keys is just as unpredictable as winter in other southern climates - it could just have easily have been 85 degrees.

We got married on a sunset dinner cruise (look up Captain Alex, Pier 2 for a great experience) on January 2nd, 2010. Key West had weather in the 80's in the few days before the wedding, but it was in the 60's while we were there! I had to wear a coat over my wedding dress after the ceremony, but considering that back home in IL it was single digits, I didn't complain! During our stay the weather was pleasant, just not hot, and we wore pants and carried a jacket most of the time. We stayed at Southern Most Point Guest House which is on Duval at the end and just 1/2 block from the beach. They have a heated pool-size jacuzzi which was fantastic. Breakfast every morning on the veranda. Great experience! Try Alonzo's on the pier between 4 and 6 pm everyday for 1/2 price drinks and appetizers!

December is one of the touchest months here in Florida. This last year was particularly cold and for a very long time, but that is not typical. If you are from a colder climate the weather shouldn't be an issue. This year was the coldest for the 20 years which I have been here. It will typically be windy that time of year but if you can get out of the wind, you shouldn't have an issue sitting in the sun.
Just about everything is open even on Christmas day, and there is usually at least one cruise ship in town. Christmas day is just another day in Key West.
Pier House is a good choice but not much of a beach. Most downtown hotel/motels don't have any beach access but great pools. I would also check out the Ocean Key Resort and Spa at Zero Duval Street. They have some great two bedroom suites. If that would work for your family. Those suites also have a small kitchen and washer/dryers. Very handy to cut down on some of the meal expenses drinks and snacks if not real meals.
The Southermost Hotel is at the exact opposite end of Duval Street, but is also great. A little out of the action but to each his/her own. Plenty of great restaurants for all price ranges. Can't really beat Key West for Christmas. Should be the warmest place on the East Coast but you will easily be able to tell the natives if it does get cool. We will be the ones in coats, boots and hats! Have fun!

You might also want to consider renting a condo in Truman Annex, which is a really nice gated area in a great location. There's are lots of realtors who deal with property there, and though I've never used any of them, one that gets good reviews is At Home in Key West.

athomekeywest.com

You may also want to consider the oil trajectories. They are saying that once the north wind starts blowing in the fall, a lot of that oil may start making its way into the Loop Current.

Again, hopefully not going to happen but once the wind direction changes in the fall, we'll see what happens. The oil has to go somewhere. In the summer, winds come from the south, pushing oil north to the Panhandle but in the winter the winds come out of the north, pushing it south. Could be a precarious time this winter.

I don't mean to dampen anyone's enthusiasm but to just keep it real. It would be a factor to consider.

We have been in the Keys twice during the Christmas season. Once it rained almost everyday and was cool, the other time we had beautiful weather. As people said it is iffy in December, but you might luck out.

We have stayed in the Southernmost properties, that FLKathleen mentioned a few times. The Southernmost Hotel on the Beach is on the opposite end of Duval from most of the action, but we always enjoyed the walk. We also stayed in the Dewey House which is owned by the same people and had a wonderful room and great service. Both have use of a small beach area.

We have also rented places in the Truman Annex as SusanCS mentioned. We really liked our places and have used www.athomeinkeywest.com and www.compassrealty.com We were pleased with both.

The only drawback to being there Christmas week, is that is very crowded and things are more expensive.