Above-average thermal gradients and temperature are observed in portions of the Gulf Coast basin. In this study, over 1,600 bottom-hole temperature measurements from south Texas were collected and analyzed. Our analysis resulted in a three-dimensional characterization of temperature distributions in a large portion of the basin in south Texas and numerical models of representative cross sections of this area. In three dimensions, the most prominent thermal feature in the south Texas subsurface is a band of high temperatures that corresponds to the Wilcox growth-fault trend. A similar but greatly subdued band corresponds to the Vicksburg-Frio growth-fault trend. Indications from temperature profiles and from modeling are that these temperature bands are controlled by the a vection of fluids from the deep basin upward along the growth-fault zone. The source of the fluids appears to be quite deep, over 12,000 ft (4,000 m) below the surface. In addition, temperatures generally increase from the northeast to the southwest within the area. This trend is presumably created by variation in basement heat flux.