Historical weather data, all-time temperature records, and monthly climate averages for San Marino, CA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4th in San Marino runs mild by local standards, with 120 years of data pointing to a typical high of 72° and low of 48°. There's a 1-in-5 chance of rain, though the date has seen wilder swings — a scorching 99° in 1989 and a bitter 35° back in 1918.
San Marino plays by Southern California's extremes: the thermometer has hit 115° as recently as September 2020, and once bottomed out at 21° in January 1913. A single March storm in 1938 dropped 7.7 inches of rain in one day, and yes — this corner of the San Gabriel Valley even saw 3 inches of snow in January 1949.
Summer is the main event here, with late July through early August averaging a toasty 90° high, while January and December are the coolest months at a mild 67°. If you're trying to avoid rain, skip late February — it's the wettest stretch of the year, averaging over an inch of precip in a single week. Spring and fall offer the sweet spot: warm, dry, and comfortable.