Historical weather data, all-time temperature records, and monthly climate averages for San Marcos, CA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4th in San Marcos runs mild, with an average high of 73° and a low of 49° across 43 years of records. But the date has some range to it — temperatures have swung from a scorching 98° in 1989 down to a frigid 35° just two years ago in 2023. Rain is unlikely, with only a 14% historical chance of precipitation.
San Marcos can get serious when it wants to — the all-time high hit a brutal 115° on September 6, 2020, and the coldest recorded day bottomed out at 25° in January 2007. The wettest single day on record dropped 3.24 inches back in January 1980, a reminder that when it rains here, it can really rain.
San Marcos stays comfortable year-round, with monthly highs ranging from a mild 68° in winter to 89° in late summer — the warmest stretch runs late August through early September. The coolest weeks fall around mid-December, though even then you're looking at average highs in the upper 60s. If you want to dodge the rain, avoid late February through early March, which is the wettest stretch of the year.