The USDA Hardiness Zones establishes a baseline of average cold temperatures over several decades of record collecting. The zones were adjusted in 2012. Listed below are the zip codes for Parker County and nearby areas. Note all of the zips are in 8A except for one.
Be aware, some areas of your landscape can have micro climates (small areas that can be cooler or warmer than the surrounding area) due to trees, lay of the land, or man made objects that could protect plants or add increase the heat in the area. Plus, a well watered soil will hold more heat than dry soil.