Thermal, CA has a population of 2,396 and is the 10,075th largest city in the United States. The population density is 255 per sq mi which is 10% higher than the California average and 182% higher than the national average. The median age in Thermal is 28 which is approximately 21% lower than the California average of 36. In Thermal, 58% of the population over 15 years of age are married, 4% speak English and 96% speak Spanish. 52% of Thermal residents were born in California, 2% were born out of state, 0% were born outside of the United States and 46% were foreign born.