Calistoga is a city in Napa County, California, United States. The population was 5,155 at the 2010 census.
According to the United States Census Bureau, the city has a total area of 2.6 square miles (6.8 km²), 99.30% of it land and 0.70% of it water.
According to National Weather Service records, Calistoga has cool, wet winters with temperatures dropping to freezing on an average of 34.1 days. Summers are usually very dry, with daytime temperature regularly reaching 90 °F (32 °C) or higher on an average of 72.8 days, but nights are cool, dropping into the lower fifties. Average January temperatures range from 59.8 °F (15.4 °C) to 36.8 °F (2.7 °C). Average July temperatures range from 92.3 °F (33.5 °C) to 53.1 °F (11.7 °C). The record high temperature of 111 °F (44 °C) occurred on July 23, 2006. The record low temperature of 12 °F (−11 °C) was recorded on December 22, 1990.