Climate averages 1991–2020
Redwood City weather
in September.
A warm, very dry month: the warmest and the 3rd driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Redwood City: daytime highs average 24.6°C and nights cool to about 14.5°C. By daytime temperature it is the warmest month of the year.
Expect about 1.8 mm of rain on fewer than one day, which makes September a very dry month (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 28 min on an average September day.
The nearest other city in this atlas is San Mateo (12 km away). In September its highs average 24.0°C, 0.7°C cooler than Redwood City, with 1.8 mm of rain.
Among the 498 cities listed in the United States, Redwood City ranks joint 325th of 498 for the warmest September highs and joint 17th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Redwood City is 2.3°C cooler than that mean.
From September to October, average highs fall by 2.5°C to 22.1°C, and monthly rainfall rises from 1.8 mm to 23 mm.
The annual picture
September 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
Redwood City climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 14.1°C6.9°C | 6.9°C | 99 | 9.4 | 9.910 h |
| February | 14.9°C7.6°C | 7.6°C | 107 | 9.5 | 10.811 h |
| March | 16.2°C8.6°C | 8.6°C | 82 | 9.1 | 11.912 h |
| April | 17.6°C9.4°C | 9.4°C | 41 | 5.6 | 13.113 h |
| May | 19.8°C10.9°C | 10.9°C | 20 | 3.3 | 14.214 h |
| June | 22.5°C12.4°C | 12.4°C | 3.9 | 0.9 | 14.715 h |
| July | 24.2°C13.9°C | 13.9°C | 0.5 | 0.2 | 14.514 h |
| August | 24.5°C14.4°C | 14.4°C | 0.7 | 0.1 | 13.614 h |
| September, selected | 24.6°C14.5°C | 14.5°C | 1.8 | 0.4 | 12.512 h |
| October | 22.1°C13.1°C | 13.1°C | 23 | 3.0 | 11.311 h |
| November | 17.2°C10.1°C | 10.1°C | 51 | 6.0 | 10.210 h |
| December | 13.8°C7.5°C | 7.5°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
September in nearby cities
- San Mateo in SeptemberUnited States · 12 kmHigh 24.0°C · Low 14.2°C · 1.8 mm rain
- Mountain View in SeptemberUnited States · 17 kmHigh 26.1°C · Low 15.0°C · 1.9 mm rain
- Sunnyvale in SeptemberUnited States · 22 kmHigh 26.7°C · Low 15.2°C · 2.5 mm rain
- Union City in SeptemberUnited States · 23 kmHigh 27.4°C · Low 15.1°C · 1.9 mm rain
- Fremont in SeptemberUnited States · 23 kmHigh 27.2°C · Low 15.4°C · 1.9 mm rain
- Hayward in SeptemberUnited States · 25 kmHigh 26.5°C · Low 14.3°C · 1.7 mm rain
- Milpitas in SeptemberUnited States · 30 kmHigh 28.0°C · Low 16.0°C · 1.9 mm rain
- Daly City in SeptemberUnited States · 32 kmHigh 20.1°C · Low 12.6°C · 1.5 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 Redwood City) is explained once on the Redwood City year overview and on the Sources, method and limits page.
San Mateo lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.