Well.... It really is difficult to tell exactly what the weather will be but odds are it will be shirtsleeve weather around Christmas. But then again I've seen it get and stay in the 'teens for a week at a time down here.
We camped the week between Christmas and New Years last year at Lake Whitney State Park and it got down to 20 degrees at night and warmed up to about 40 degrees during the day with drizzle the entire week.
The only problem we had was with the water hose freezing cause I failed to remember the heat strip for it when we left home. I just filled the freshwater tank and disconnected the hose at night.
We burned pretty close to two tanks of propane but never had to use the reserve tank I bring during the winter.
One thing I don't leave the grey water drains open when it's gonna freeze.
Only thing I can tell you about central Texas weather is to expect the Blue Norther but bring tee shirts and shorts too..
Heck, I typed all that and then seen you was from Abilene so you should already know what to expect.
Doing the RV thing since 1982
2020 Avalanche 313 RS 15K GVWR
2015 F350 6.7 2WD Dually 6062 Payload
B&W 25K RVK3305 Companion Hitch
63 Gallon RDS Wedge Aux Tank
Plenty of truck...and now plenty of hitch, WI-FI & fuel