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San Mateo Weather by Month
Average temperatures, rainfall and humidity for San Mateo, United States, month by month, built from OpenWeather's historical records. Use it to see what a typical San Mateo month looks like before you travel — then check the live San Mateo forecast for the days ahead.
Warmest month
September
24°C average high
Coolest month
December
8°C average low
Wettest month
December
97 mm of rain
Driest month
September
12 mm of rain
Average temperature and rainfall in San Mateo by month
Averages of the daily highs and lows recorded in each month, with total rainfall, mean humidity and mean wind speed.
| Month | Avg high | Avg low | Record low / high | Rainfall | Humidity | Wind |
|---|---|---|---|---|---|---|
| January | 15°C | 8°C | 1°C / 24°C | 73 mm | 76% | 12 km/h |
| February | 16°C | 8°C | 0°C / 24°C | 64 mm | 75% | 15 km/h |
| March | 17°C | 9°C | 2°C / 26°C | 63 mm | 76% | 16 km/h |
| April | 18°C | 10°C | 4°C / 30°C | 42 mm | 75% | 18 km/h |
| May | 19°C | 11°C | 6°C / 31°C | 27 mm | 77% | 19 km/h |
| June | 21°C | 12°C | 9°C / 36°C | 18 mm | 78% | 17 km/h |
| July | 22°C | 13°C | 10°C / 35°C | 15 mm | 80% | 16 km/h |
| August | 23°C | 14°C | 12°C / 36°C | 12 mm | 81% | 16 km/h |
| September | 24°C | 14°C | 10°C / 40°C | 12 mm | 78% | 14 km/h |
| October | 22°C | 12°C | 7°C / 36°C | 19 mm | 73% | 12 km/h |
| November | 18°C | 10°C | 3°C / 28°C | 47 mm | 75% | 12 km/h |
| December | 14°C | 8°C | 0°C / 28°C | 97 mm | 77% | 13 km/h |
Best time to visit San Mateo
The most comfortable time to visit San Mateo is generally July to September, balancing mild daytime temperatures against the driest stretch of the year. The city has a moderate seasonal swing and rain concentrates around December, totalling about 488 mm a year.
Travellers who prefer heat should aim for September, when highs average 24°C. December is the month to avoid if rain would spoil your plans — it averages 97 mm, roughly 8× the rainfall of September.
Source: OpenWeather historical and statistical weather data. Values are long-term averages, not a forecast — see the San Mateo forecast for what is happening now.