we went to vegas a few years ago,on the 1st & i would say,it wasn't warm enough,for the oudoor pool.can't help with san diego,sorry.
tracy

I have read several people say that Vegas is cold December and January. They had several inches of snow last December which, although unusual, isn't impossible. I doubt that the outside pools would be open.

luci

Have been to Vegas in December (Christmas) for the last 2 years, last year cold, snow, rain at times and cloudy, the previous year it was blue sky and sunshine alot of the time but cold, there is no way in this world I would even think about going in an outside pool in those temperatures!

Thanks for the replies, looks like Florida it is then !!

Vegas will be cold, and all the pools closed, however San diego will be in the 70,s and fine it,s a great city I think

Hi

Just came back from Vegas yesterday and the weather was very nice and very warm!

Never needed a jacket at all. Bellagio pools were busy every day

Hope thst helps