You can get anything from below freezing to 80 degrees, no matter how much research you do you will not know til it gets here.
The first Xmas we spent out there was 2000, absolutely freezing every day, had to de-ice car, buy fleeces, hats, wearing socks on our hands under the gloves etc. Other 4 times not as bad but still the odd cold spell, I remember Xmas 2004 getting out of the heated pool at Hilton DTD to find no towels, we were stood there frozen solid, DS had to run into the hotel to find towels.
Had some great hot days at Xmas but just go prepared for all weather & temps.