Climate averages 1991–2020
San Mateo weather
in April.
A mild, moderately wet month: the 7th warmest and the 7th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
April is a mild month in San Mateo: daytime highs average 17.4°C and nights cool to about 9.3°C. By daytime temperature it is the 7th warmest of the 12 months.
Expect about 41 mm of rain on roughly 6 days, which makes April a moderately wet month (the 7th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 08 min on an average April day.
The nearest other city in this atlas is Redwood City (12 km away). In April its highs average 17.6°C, about as warm as San Mateo, with 41 mm of rain.
Among the 498 cities listed in the United States, San Mateo ranks joint 306th of 498 for the warmest April highs and joint 126th of 498 for the driest April (rainfall, lowest first). The mean April high of those 498 cities is 19.4°C; San Mateo is 2.0°C cooler than that mean.
From April to May, average highs rise by 2.0°C to 19.3°C, and monthly rainfall falls from 41 mm to 20 mm.
The annual picture
April in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
San Mateo climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 13.9°C6.7°C | 6.7°C | 99 | 9.4 | 9.910 h |
| February | 14.8°C7.5°C | 7.5°C | 107 | 9.5 | 10.811 h |
| March | 16.1°C8.5°C | 8.5°C | 82 | 9.1 | 11.912 h |
| April, selected | 17.4°C9.3°C | 9.3°C | 41 | 5.6 | 13.113 h |
| May | 19.3°C10.9°C | 10.9°C | 20 | 3.3 | 14.214 h |
| June | 21.8°C12.4°C | 12.4°C | 3.9 | 0.9 | 14.715 h |
| July | 23.2°C13.7°C | 13.7°C | 0.5 | 0.2 | 14.514 h |
| August | 23.6°C14.2°C | 14.2°C | 0.7 | 0.1 | 13.614 h |
| September | 24.0°C14.2°C | 14.2°C | 1.8 | 0.4 | 12.512 h |
| October | 21.7°C12.9°C | 12.9°C | 23 | 3.0 | 11.311 h |
| November | 17.0°C9.9°C | 9.9°C | 51 | 6.0 | 10.210 h |
| December | 13.7°C7.2°C | 7.2°C | 94 | 9.3 | 9.610 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
April in nearby cities
- Redwood City in AprilUnited States · 12 kmHigh 17.6°C · Low 9.4°C · 41 mm rain
- Daly City in AprilUnited States · 20 kmHigh 15.1°C · Low 8.7°C · 37 mm rain
- Hayward in AprilUnited States · 25 kmHigh 18.9°C · Low 9.0°C · 33 mm rain
- San Francisco in AprilUnited States · 25 kmHigh 17.0°C · Low 8.8°C · 37 mm rain
- Union City in AprilUnited States · 27 kmHigh 19.1°C · Low 9.2°C · 40 mm rain
- Oakland in AprilUnited States · 27 kmHigh 18.9°C · Low 8.9°C · 34 mm rain
- Mountain View in AprilUnited States · 29 kmHigh 18.3°C · Low 9.3°C · 40 mm rain
- Fremont in AprilUnited States · 30 kmHigh 18.9°C · Low 9.3°C · 40 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for San Mateo) is explained once on the San Mateo year overview and on the Sources, method and limits page.
Redwood City lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.