Thermalito, California, United States [CDP]; population was 5,646 in 1990; housing units was 2,184 in 1990; location is 39°29'N 121°36'W; land area is 12.94 square miles (8,279 acres); water area is 0.14 square miles (90 acres); FIPS code is 78470 [SourceCBP]