Very timingly question. I am living at SF Bay Area, It supposes nice warmer in the Winter. No! My house is located at middle of hill. I have ice sheet formation in water bucket about 3/8 inch thick. My plants all in pots are all okay.

I do not think you should worry about in Huston. But you should keep your camellia well watered.

Camellia japonica are also found in nature at eastern China region. There are also many millions of camellia grown in pots in their nuseries. The area weather always has some snow and occasional ice formation.

If you have a red camellia in bloom under thick snow fall, you should take a picture for red and white coloration.

They do quite well here in Northern Alabama, where the temperatures dip into the low 20s routinely, every winter. Soft flower buds, showing color, would likely get zapped at those temperatures, but they are really much hardier than you think.