San Gregorio has a cool summer Mediterranean climate. A National Weather Service cooperative weather station has been in operation in San Gregorio since June 1, 1954. San Gregorio enjoys mild weather throughout the year, except for some remarkably chilly mornings, even in the summer. Fog and low overcast are common in the night and morning hours, too, especially in the summer. The fog usually clears to the shoreline by the afternoon. Temperatures are often much warmer just a few miles inland than on the coast. Most of the rainfall falls from November through April. Normal annual precipitation is 29.52 inches. San Gregorio has an average of 92.3 days with measurable rain. The wettest year on record was 1983 when 57.86 inches of rain fell. The wettest month recorded was 12.13 inches in February 1998. The maximum 24-hour rainfall was 6.87 inches on December 23, 1955. Although snow is very rare in the coastal lowlands, 4.0 inches fell in San Gregorio on January 21, 1962. January is the coolest month with an average high of 60.1 °F and an average low of 40.3 °F. September is the warmest month with an average high of 72.5 °F and an average low of 49.3 °F. The highest temperature on record was 99 °F on October 5, 1987. The lowest temperature on record was 20 °F on December 20, 1998. Temperatures exceed 90 °F on an average of only 1.8 days, but have occurred in April, May, June, July, August, September, and October. Freezing temperatures or below are more common, occurring on an average of 13.1 days, and have been recorded in January, February, March, April, May, June, October, November, and December.
History
The first European land exploration of Alta California, the Spanish Portolà expedition, passed through the area on its way north, camping for three days near today's San Gregorio, October 24–26, 1769. Franciscan missionary Juan Crespi noted in his diary, "This is a fine place, with good lands and an abundance of water, where a good mission could be placed". No mission was ever established here, however. The string of Spanish Missions established over the next 50 years followed a more inland route through San Jose. During the Mexican era, the area was part of Rancho San Gregoria. Named after Pope Gregory I. San Gregorio was a booming town in the 1850s, when wealthy San Franciscans would travel to the San Gregorio House by stagecoach to enjoy fishing, hunting, sea bathing, and boat races. The building still stands, but is no longer a functioning hotel. In the nineteenth century, a Chinese community had lived along the creek which runs through San Gregorio however, the buildings of the former community were washed away due to heavy rains. The San Gregorio General Store has been operating since 1889. The original stagecoach stop stands across Highway 84 from the store. In 1915, the community was home to seven cheese factories. San Gregorio has been the site of several film locations and television show episode scenes.
