From the Houston/Galveston National Weather Service:

Snowy weather across southeast Texas is a rare phenomenon. If certain weather elements are in phase, it can snow in Southeast Texas. These elements came together for a significant snow event on Christmas Eve 2004 across most of Southeast Texas. Snow flurries fluttered to the ground during the day on the 24th with heavier snow developing on Christmas Eve and during the early morning hours of Christmas Day. Galveston received 4.0 inches of snow on the 24th and 25th. Areas south of I-10 received heavier snow with 6 to 10 inches of snow falling from Victoria to Wharton to Alvin.