Climate averages 1991–2020
Hayward weather
in September.
A warm, very dry month: the joint 2nd 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 Hayward: daytime highs average 26.5°C and nights cool to about 14.3°C. By daytime temperature it is the joint 2nd warmest of the 12 months.
Expect about 1.7 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 Union City (10 km away). In September its highs average 27.4°C, 1.0°C warmer than Hayward, with 1.9 mm of rain.
Among the 498 cities listed in the United States, Hayward ranks joint 258th of 498 for the warmest September highs and joint 11th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Hayward is 0.4°C cooler than that mean.
From September to October, average highs fall by 3.3°C to 23.2°C, and monthly rainfall rises from 1.7 mm to 21 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
Hayward climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 14.0°C5.8°C | 5.8°C | 89 | 8.9 | 9.910 h |
| February | 15.2°C6.8°C | 6.8°C | 94 | 9.0 | 10.811 h |
| March | 17.0°C8.0°C | 8.0°C | 70 | 8.4 | 11.912 h |
| April | 18.9°C9.0°C | 9.0°C | 33 | 4.8 | 13.113 h |
| May | 21.7°C10.8°C | 10.8°C | 17 | 3.0 | 14.214 h |
| June | 24.9°C12.7°C | 12.7°C | 3.4 | 0.9 | 14.715 h |
| July | 26.5°C14.1°C | 14.1°C | 0.7 | 0.2 | 14.514 h |
| August | 26.7°C14.5°C | 14.5°C | 1.4 | 0.2 | 13.614 h |
| September, selected | 26.5°C14.3°C | 14.3°C | 1.7 | 0.4 | 12.512 h |
| October | 23.2°C12.5°C | 12.5°C | 21 | 2.9 | 11.311 h |
| November | 17.5°C9.0°C | 9.0°C | 42 | 5.5 | 10.210 h |
| December | 13.8°C6.2°C | 6.2°C | 81 | 8.7 | 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
- Union City in SeptemberUnited States · 10 kmHigh 27.4°C · Low 15.1°C · 1.9 mm rain
- San Ramon in SeptemberUnited States · 15 kmHigh 27.4°C · Low 14.1°C · 1.7 mm rain
- Fremont in SeptemberUnited States · 16 kmHigh 27.2°C · Low 15.4°C · 1.9 mm rain
- Pleasanton in SeptemberUnited States · 18 kmHigh 28.0°C · Low 14.4°C · 1.7 mm rain
- Oakland in SeptemberUnited States · 23 kmHigh 26.2°C · Low 13.8°C · 1.4 mm rain
- San Mateo in SeptemberUnited States · 25 kmHigh 24.0°C · Low 14.2°C · 1.8 mm rain
- Redwood City in SeptemberUnited States · 25 kmHigh 24.6°C · Low 14.5°C · 1.8 mm rain
- Livermore in SeptemberUnited States · 28 kmHigh 28.3°C · Low 14.3°C · 1.7 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 Hayward) is explained once on the Hayward year overview and on the Sources, method and limits page.
San Ramon lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.