September is one of the warmer months of the year in Hayward, with average highs near 29.5°C and lows around 12.1°C (mean 20.8°C). It is one of the drier months, averaging 6 mm of rainfall and 61% relative humidity across the period.
September is one of the warmer months of the year in Hayward. Across 45 years of records, the warmest September in Hayward was 1984 — when the month averaged 23.1°C — while the coldest was 1986 at 17.4°C. Typical September days reach 29.5°C with nights near 12.1°C. The long-term trend is warming, about 0.2°C per decade.
September is one of the drier months in Hayward, averaging 6 mm of rainfall. The wettest September on record was 1989 with 35 mm, while the driest were 2011, 2012 and 2020, among others at 0 mm.
Relative humidity in Hayward during September averages 61%. The most humid September was 2023 at 72%, and the least humid was 1984 at 46%.
September receives about 5 kWh/m²/day of solar energy in Hayward. The sunniest September was 1997 at 5.9 kWh/m²/day, and the cloudiest was 1991 at 4.1.
Average wind speed in Hayward during September is 2.1 m/s. The windiest Septembers were 2013, 2019 and 2023 at 2.4 m/s, while the calmest was 1991 at 1.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 20.2°C | 21.0°C | 20.7°C | 21.0°C | 21.4°C | +1.2°C |
| Avg High | 28.9°C | 30.0°C | 29.5°C | 29.5°C | 29.9°C | +1°C |
| Avg Low | 11.5°C | 11.9°C | 11.9°C | 12.5°C | 12.9°C | +1.4°C |
| Avg Rain | 16 mm | 2 mm | 4 mm | 3 mm | 6 mm | -10 mm |
September temperatures in Hayward have risen by about 0.5°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 6.8°C (1985) to a record high of 46°C (2022).
Rainfall in September is one of the drier months, averaging 6 mm, with a wettest year of 35 mm.
One of the best times to visit Hayward
September is one of the best times to visit Hayward. Expect days averaging 29.5°C and nights around 12.1°C (mean 20.8°C) — warmer than Hayward's yearly average — with low rainfall (6 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 29.3°C | 21.6°C | 13.9°C | 39.7°C | 12.1°C | 8 mm | 67% | 2.2 m/s | 4.7 |
| 2024 | 30.7°C | 21.5°C | 12.4°C | 39.6°C | 10.0°C | 0 mm | 61% | 2.1 m/s | 5.1 |
| 2023 | 26.9°C | 19.3°C | 11.7°C | 32.8°C | 8.8°C | 2 mm | 72% | 2.4 m/s | 5 |
| 2022 | 30.7°C | 22.4°C | 14.0°C | 46.0°C | 8.7°C | 20 mm | 60% | 2.1 m/s | 5.2 |
| 2021 | 29.9°C | 20.9°C | 11.8°C | 37.7°C | 8.8°C | 2 mm | 60% | 2.2 m/s | 5 |
| 2020 | 31.6°C | 22.5°C | 13.3°C | 44.8°C | 9.9°C | 0 mm | 60% | 1.9 m/s | 4.9 |
| 2019 | 28.7°C | 20.9°C | 13.2°C | 38.2°C | 7.2°C | 5 mm | 63% | 2.4 m/s | 5.7 |
| 2018 | 29.2°C | 19.9°C | 10.6°C | 37.2°C | 8.5°C | 0 mm | 63% | 2.2 m/s | 5.2 |
| 2017 | 30.1°C | 22.3°C | 14.5°C | 44.8°C | 8.9°C | 2 mm | 58% | 2.2 m/s | 5 |
| 2016 | 29.2°C | 20.7°C | 12.1°C | 38.5°C | 9.5°C | 0 mm | 59% | 2.3 m/s | 5.3 |
| 2015 | 29.8°C | 21.9°C | 14.0°C | 40.1°C | 10.2°C | 2 mm | 55% | 2.1 m/s | 5.2 |
| 2014 | 29.5°C | 21.2°C | 12.9°C | 37.1°C | 9.6°C | 11 mm | 68% | 2 m/s | 4.9 |
| 2013 | 27.4°C | 19.7°C | 11.9°C | 37.0°C | 6.9°C | 11 mm | 68% | 2.4 m/s | 5.4 |
| 2012 | 29.3°C | 19.8°C | 10.3°C | 37.1°C | 8.4°C | 0 mm | 64% | 2.2 m/s | 4.9 |
| 2011 | 31.4°C | 22.2°C | 12.9°C | 38.7°C | 9.2°C | 0 mm | 57% | 2 m/s | 4.9 |
| 2010 | 30.3°C | 21.4°C | 12.5°C | 40.8°C | 7.9°C | 1 mm | 57% | 2 m/s | 5.3 |
| 2009 | 31.0°C | 21.9°C | 12.8°C | 38.9°C | 7.2°C | 10 mm | 60% | 2.1 m/s | 5.2 |
| 2008 | 31.1°C | 21.6°C | 12.0°C | 39.3°C | 7.9°C | 1 mm | 56% | 1.9 m/s | 5.1 |
| 2007 | 26.8°C | 19.2°C | 11.5°C | 38.0°C | 7.4°C | 7 mm | 64% | 2.2 m/s | 5.2 |
| 2006 | 29.9°C | 20.6°C | 11.2°C | 38.3°C | 7.7°C | 1 mm | 59% | 2 m/s | 4.7 |
| 2005 | 27.2°C | 18.9°C | 10.6°C | 36.0°C | 8.1°C | 3 mm | 63% | 2.1 m/s | 4.8 |
| 2004 | 29.9°C | 21.1°C | 12.3°C | 39.6°C | 7.7°C | 3 mm | 55% | 2.2 m/s | 5.7 |
| 2003 | 30.6°C | 22.0°C | 13.3°C | 40.9°C | 9.5°C | 1 mm | 58% | 2.1 m/s | 5.1 |
| 2002 | 30.3°C | 21.4°C | 12.6°C | 39.0°C | 8.0°C | 1 mm | 55% | 2.1 m/s | 5.3 |
| 2001 | 28.7°C | 19.8°C | 11.0°C | 39.3°C | 9.3°C | 4 mm | 66% | 2.3 m/s | 4.7 |
| 2000 | 29.5°C | 20.8°C | 12.0°C | 39.3°C | 8.5°C | 7 mm | 60% | 2 m/s | 5.2 |
| 1999 | 31.1°C | 21.4°C | 11.6°C | 36.9°C | 9.1°C | 3 mm | 57% | 2 m/s | 4.6 |
| 1998 | 28.9°C | 21.0°C | 13.0°C | 40.5°C | 9.4°C | 4 mm | 63% | 2.3 m/s | 4.9 |
| 1997 | 30.4°C | 21.9°C | 13.3°C | 38.1°C | 10.8°C | 1 mm | 60% | 2.2 m/s | 5.9 |
| 1996 | 29.0°C | 19.8°C | 10.7°C | 35.6°C | 8.2°C | 2 mm | 60% | 2.1 m/s | 4.9 |
| 1995 | 28.8°C | 20.1°C | 11.3°C | 38.7°C | 8.8°C | 0 mm | 66% | 2.2 m/s | 5.1 |
| 1994 | 29.7°C | 20.9°C | 12.0°C | 37.0°C | 9.3°C | 2 mm | 63% | 2 m/s | 4.8 |
| 1993 | 30.2°C | 21.1°C | 11.9°C | 37.6°C | 7.6°C | 1 mm | 58% | 1.9 m/s | 4.9 |
| 1992 | 30.4°C | 21.1°C | 11.9°C | 36.1°C | 8.5°C | 1 mm | 59% | 2.1 m/s | 5.1 |
| 1991 | 31.5°C | 21.7°C | 11.9°C | 38.2°C | 8.8°C | 2 mm | 60% | 1.8 m/s | 4.1 |
| 1990 | 29.5°C | 20.6°C | 11.7°C | 35.8°C | 9.8°C | 8 mm | 66% | 2.1 m/s | 5.4 |
| 1989 🌧️ | 27.3°C | 19.0°C | 10.7°C | 35.7°C | 8.3°C | 35 mm | 65% | 1.9 m/s | 4.7 |
| 1988 | 31.1°C | 20.9°C | 10.8°C | 41.9°C | 8.1°C | 0 mm | 53% | 2 m/s | 4.7 |
| 1987 | 30.7°C | 21.3°C | 11.9°C | 37.8°C | 9.6°C | 0 mm | 57% | 2.1 m/s | 4.5 |
| 1986 ❄️ | 25.0°C | 17.4°C | 9.8°C | 35.8°C | 7.7°C | 30 mm | 66% | 2.2 m/s | 4.9 |
| 1985 | 26.5°C | 18.6°C | 10.8°C | 34.6°C | 6.8°C | 10 mm | 64% | 2 m/s | 4.9 |
| 1984 🔥 | 32.5°C | 23.1°C | 13.8°C | 39.4°C | 8.1°C | 2 mm | 46% | 2 m/s | 5.6 |
| 1983 | 30.8°C | 22.0°C | 13.1°C | 39.2°C | 9.1°C | 28 mm | 58% | 2 m/s | — |
| 1982 | 27.5°C | 19.3°C | 11.1°C | 36.9°C | 7.3°C | 34 mm | 60% | 2.1 m/s | — |
| 1981 | 29.1°C | 20.1°C | 11.1°C | 35.6°C | 7.9°C | 3 mm | 61% | 2.2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 29.5°C with lows near 12.1°C (mean 20.8°C), based on 45 years of NASA POWER data.
September averages 6 mm of rainfall in Hayward, one of the drier months. The wettest on record was 35 mm in 1989.
The hottest September reached 46°C in 2022. The coldest dipped to 6.8°C in 1985.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 0.5°C. Daytime highs moved from 29.3°C to 29.5°C and overnight lows from 12°C to 12.8°C over the same span.
September is one of the warmer months of the year in Hayward and one of the drier months, so plan for around 29.5°C daytime highs and 12.1°C at night.
Not quite — September is the 10th coolest month in Hayward, averaging 20.8°C.
For September in Hayward, pack light layers you can adjust through the day, with typical highs of 29.5°C and lows of 12.1°C.
Relative humidity in September averages 61% — moderately humid.
Average wind speed in September is 2.1 m/s. The windiest September on record averaged 2.4 m/s (2013).
The wettest September on record was 1989 with 35 mm. On average, September sees 6 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Hayward behaves each September, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for September specifically, along with year-by-year records and how the month has changed over the decades.
