September is one of the warmer months of the year in San Tan Valley, with average highs near 35.6°C and lows around 21.1°C (mean 28.4°C). It is about average for rainfall, averaging 30 mm of rainfall and 37% relative humidity across the period.
September is one of the warmer months of the year in San Tan Valley. Across 45 years of records, the warmest September in San Tan Valley was 2024 — when the month averaged 31.2°C — while the coldest was 1985 at 25°C. Typical September days reach 35.6°C with nights near 21.1°C. The long-term trend is warming, about 0.6°C per decade.
September is about average for rainfall in San Tan Valley, averaging 30 mm of rainfall. The wettest September on record was 1983 with 133 mm, while the driest was 2020 at 1 mm.
Relative humidity in San Tan Valley during September averages 37%. The most humid September was 1983 at 53%, and the least humid was 2020 at 23%.
September receives about 6 kWh/m²/day of solar energy in San Tan Valley. The sunniest Septembers were 1993 and 2001 at 6.5 kWh/m²/day, and the cloudiest were 1984, 2015 and 2025 at 5.6.
Average wind speed in San Tan Valley during September is 2.1 m/s. The windiest Septembers were 1984 and 1989 at 2.6 m/s, while the calmest was 2021 at 1.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 27.2°C | 28.0°C | 28.5°C | 28.8°C | 29.8°C | +2.6°C |
| Avg High | 34.5°C | 35.1°C | 35.9°C | 35.7°C | 37.0°C | +2.5°C |
| Avg Low | 19.8°C | 20.8°C | 21.1°C | 21.8°C | 22.6°C | +2.8°C |
| Avg Rain | 44 mm | 33 mm | 22 mm | 29 mm | 19 mm | -25 mm |
September temperatures in San Tan Valley have risen by about 2.2°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 10.4°C (1986) to a record high of 44.1°C (2020).
Rainfall in September is about average for rainfall, averaging 30 mm, with a wettest year of 133 mm.
A good time to visit San Tan Valley
September is a good time to visit San Tan Valley, with days averaging 35.6°C and nights around 21.1°C (mean 28.4°C, warmer than San Tan Valley's yearly average) and moderate rainfall. October and May are marginally more temperate, but September still suits most travellers.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 35.8°C | 29.2°C | 22.5°C | 39.7°C | 17.9°C | 39 mm | 44% | 1.7 m/s | 5.6 |
| 2024 🔥 | 38.9°C | 31.2°C | 23.4°C | 43.6°C | 17.0°C | 4 mm | 24% | 2.4 m/s | 6.4 |
| 2023 | 37.3°C | 29.8°C | 22.3°C | 42.6°C | 19.2°C | 17 mm | 27% | 2 m/s | 6.1 |
| 2022 | 36.3°C | 29.5°C | 22.7°C | 40.3°C | 19.4°C | 28 mm | 44% | 2 m/s | 5.9 |
| 2021 | 35.5°C | 28.8°C | 22.1°C | 40.5°C | 17.7°C | 27 mm | 43% | 1.6 m/s | 5.8 |
| 2020 | 38.1°C | 30.4°C | 22.7°C | 44.1°C | 15.5°C | 1 mm | 23% | 2.2 m/s | 6.2 |
| 2019 | 35.5°C | 28.9°C | 22.3°C | 42.5°C | 17.2°C | 41 mm | 41% | 2 m/s | 5.8 |
| 2018 | 37.2°C | 30.4°C | 23.6°C | 41.6°C | 20.5°C | 26 mm | 33% | 1.8 m/s | 6.3 |
| 2017 | 35.9°C | 28.3°C | 20.7°C | 41.6°C | 12.8°C | 4 mm | 28% | 2.3 m/s | 6.4 |
| 2016 | 34.3°C | 27.5°C | 20.6°C | 39.2°C | 13.8°C | 22 mm | 37% | 2.2 m/s | 5.7 |
| 2015 | 35.3°C | 29.0°C | 22.7°C | 39.3°C | 20.1°C | 24 mm | 44% | 1.8 m/s | 5.6 |
| 2014 | 34.8°C | 28.5°C | 22.2°C | 39.8°C | 14.8°C | 69 mm | 48% | 1.9 m/s | 5.9 |
| 2013 | 35.3°C | 28.3°C | 21.3°C | 41.3°C | 12.4°C | 27 mm | 38% | 2.1 m/s | 6 |
| 2012 | 34.7°C | 27.9°C | 21.2°C | 39.3°C | 16.8°C | 29 mm | 41% | 2 m/s | 5.8 |
| 2011 | 37.0°C | 29.5°C | 22.0°C | 41.8°C | 18.1°C | 31 mm | 32% | 2 m/s | 6.1 |
| 2010 | 37.4°C | 29.6°C | 21.8°C | 41.1°C | 16.4°C | 20 mm | 32% | 2 m/s | 6.4 |
| 2009 | 35.7°C | 28.6°C | 21.5°C | 39.7°C | 17.6°C | 30 mm | 34% | 2.1 m/s | 6.2 |
| 2008 | 35.4°C | 28.2°C | 21.0°C | 39.7°C | 17.2°C | 18 mm | 39% | 2.2 m/s | 6.4 |
| 2007 | 35.3°C | 28.3°C | 21.3°C | 39.7°C | 14.4°C | 20 mm | 38% | 2 m/s | 6.1 |
| 2006 | 32.8°C | 25.8°C | 18.8°C | 38.4°C | 13.7°C | 30 mm | 43% | 2.2 m/s | 6.1 |
| 2005 | 36.0°C | 28.5°C | 21.0°C | 39.7°C | 15.1°C | 17 mm | 32% | 2 m/s | 6.1 |
| 2004 | 35.4°C | 27.7°C | 19.9°C | 40.8°C | 12.1°C | 34 mm | 32% | 2.3 m/s | 6.3 |
| 2003 | 36.8°C | 29.4°C | 21.9°C | 41.3°C | 17.9°C | 29 mm | 34% | 2.1 m/s | 6 |
| 2002 | 36.1°C | 28.8°C | 21.5°C | 41.6°C | 15.1°C | 30 mm | 35% | 2.3 m/s | 6 |
| 2001 | 37.8°C | 30.0°C | 22.2°C | 41.1°C | 18.1°C | 6 mm | 27% | 2.5 m/s | 6.5 |
| 2000 | 37.6°C | 29.8°C | 21.9°C | 42.5°C | 15.9°C | 7 mm | 28% | 2.2 m/s | 6.2 |
| 1999 | 35.8°C | 28.5°C | 21.2°C | 39.4°C | 17.6°C | 32 mm | 41% | 2.2 m/s | 6 |
| 1998 | 36.3°C | 28.7°C | 21.1°C | 39.9°C | 15.6°C | 31 mm | 35% | 2.3 m/s | 5.9 |
| 1997 | 37.0°C | 30.1°C | 23.1°C | 40.7°C | 17.7°C | 23 mm | 39% | 1.9 m/s | 5.8 |
| 1996 | 32.7°C | 26.0°C | 19.3°C | 37.4°C | 13.8°C | 59 mm | 47% | 1.8 m/s | 5.8 |
| 1995 | 35.5°C | 28.6°C | 21.7°C | 41.4°C | 13.1°C | 35 mm | 39% | 2 m/s | 6.2 |
| 1994 | 34.9°C | 28.2°C | 21.6°C | 38.9°C | 16.6°C | 45 mm | 41% | 1.7 m/s | 5.8 |
| 1993 | 35.2°C | 27.0°C | 18.9°C | 38.7°C | 13.3°C | 13 mm | 37% | 2.2 m/s | 6.5 |
| 1992 | 35.4°C | 27.8°C | 20.3°C | 38.3°C | 16.6°C | 17 mm | 38% | 2.1 m/s | 6.3 |
| 1991 | 34.3°C | 27.3°C | 20.2°C | 38.5°C | 15.5°C | 25 mm | 40% | 2.2 m/s | 5.9 |
| 1990 | 34.0°C | 27.3°C | 20.7°C | 39.7°C | 15.7°C | 45 mm | 50% | 1.8 m/s | 5.8 |
| 1989 | 36.6°C | 28.6°C | 20.6°C | 40.1°C | 14.7°C | 6 mm | 25% | 2.6 m/s | 6.3 |
| 1988 | 34.5°C | 26.4°C | 18.2°C | 38.3°C | 13.4°C | 9 mm | 35% | 2.4 m/s | 6.2 |
| 1987 | 34.1°C | 26.6°C | 19.2°C | 38.8°C | 13.6°C | 26 mm | 34% | 2.2 m/s | 5.8 |
| 1986 | 33.1°C | 25.4°C | 17.7°C | 39.5°C | 10.4°C | 22 mm | 38% | 2.3 m/s | 5.8 |
| 1985 ❄️ | 32.2°C | 25.0°C | 17.7°C | 37.4°C | 12.5°C | 70 mm | 41% | 2.4 m/s | 5.8 |
| 1984 | 34.7°C | 27.7°C | 20.7°C | 39.7°C | 16.7°C | 56 mm | 48% | 2.6 m/s | 5.6 |
| 1983 🌧️ | 34.8°C | 28.7°C | 22.6°C | 40.8°C | 16.8°C | 133 mm | 53% | 1.9 m/s | — |
| 1982 | 34.6°C | 27.4°C | 20.2°C | 41.0°C | 12.2°C | 50 mm | 44% | 2.3 m/s | — |
| 1981 | 36.2°C | 28.8°C | 21.4°C | 39.0°C | 16.8°C | 26 mm | 34% | 2.2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 35.6°C with lows near 21.1°C (mean 28.4°C), based on 45 years of NASA POWER data.
September averages 30 mm of rainfall in San Tan Valley, about average for rainfall. The wettest on record was 133 mm in 1983.
The hottest September reached 44.1°C in 2020. The coldest dipped to 10.4°C in 1986.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.2°C. Daytime highs moved from 34.5°C to 36.8°C and overnight lows from 20.5°C to 22.6°C over the same span.
September is one of the warmer months of the year in San Tan Valley and about average for rainfall, so plan for around 35.6°C daytime highs and 21.1°C at night.
Not quite — September is the 9th coolest month in San Tan Valley, averaging 28.4°C.
For September in San Tan Valley, pack light, breathable clothing and sun protection, with typical highs of 35.6°C and lows of 21.1°C.
Relative humidity in September averages 37% — relatively dry.
Average wind speed in September is 2.1 m/s. The windiest September on record averaged 2.6 m/s (1984).
The wettest September on record was 1983 with 133 mm. On average, September sees 30 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 San Tan Valley 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.
