September is one of the warmer months of the year in Stevenage, with average highs near 19.3°C and lows around 9.9°C (mean 14.6°C). It is about average for rainfall, averaging 53 mm of rainfall and 81% relative humidity across the period.
September is one of the warmer months of the year in Stevenage. Across 45 years of records, the warmest September in Stevenage was 2023 — when the month averaged 18.1°C — while the coldest was 1986 at 11.6°C. Typical September days reach 19.3°C with nights near 9.9°C. The long-term trend is warming, about 0.4°C per decade.
September is about average for rainfall in Stevenage, averaging 53 mm of rainfall. The wettest September on record was 2000 with 102 mm, while the driest was 2014 at 17 mm.
Relative humidity in Stevenage during September averages 81%. The most humid September was 2000 at 86%, and the least humid was 1990 at 74%.
September receives about 3.2 kWh/m²/day of solar energy in Stevenage. The sunniest September was 1991 at 3.6 kWh/m²/day, and the cloudiest was 2000 at 2.6.
Average wind speed in Stevenage during September is 3.2 m/s. The windiest September was 1983 at 4 m/s, while the calmest was 2014 at 2.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.0°C | 14.2°C | 14.8°C | 14.5°C | 15.8°C | +1.8°C |
| Avg High | 18.6°C | 18.7°C | 19.4°C | 19.4°C | 20.7°C | +2.1°C |
| Avg Low | 9.4°C | 9.6°C | 10.1°C | 9.7°C | 10.9°C | +1.5°C |
| Avg Rain | 49 mm | 67 mm | 50 mm | 46 mm | 51 mm | +2 mm |
September temperatures in Stevenage have risen by about 1.7°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 2.5°C (2003) to a record high of 30.8°C (2023).
Rainfall in September is about average for rainfall, averaging 53 mm, with a wettest year of 102 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.5°C per decade while lows rose 0.3°C per decade, widening the gap between day and night.
One of the best times to visit Stevenage
September is one of the best times to visit Stevenage. Expect days averaging 19.3°C and nights around 9.9°C (mean 14.6°C) — warmer than Stevenage's yearly average — with moderate rainfall (53 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 | 20.1°C | 15.1°C | 10.1°C | 27.0°C | 5.3°C | 40 mm | 77% | 3.9 m/s | 3.4 |
| 2024 | 19.5°C | 15.0°C | 10.5°C | 26.3°C | 3.8°C | 82 mm | 84% | 3.2 m/s | 2.9 |
| 2023 🔥 | 23.2°C | 18.1°C | 12.9°C | 30.8°C | 8.1°C | 50 mm | 80% | 2.9 m/s | 3.3 |
| 2022 | 19.9°C | 15.3°C | 10.6°C | 25.1°C | 5.2°C | 43 mm | 79% | 2.8 m/s | 3 |
| 2021 | 21.2°C | 16.3°C | 11.4°C | 27.3°C | 6.0°C | 46 mm | 84% | 2.7 m/s | 3.2 |
| 2020 | 20.1°C | 14.9°C | 9.7°C | 27.0°C | 4.9°C | 46 mm | 79% | 3.3 m/s | 3.5 |
| 2019 | 20.0°C | 14.9°C | 9.8°C | 24.7°C | 5.3°C | 81 mm | 78% | 3.4 m/s | 3.4 |
| 2018 | 19.7°C | 14.6°C | 9.5°C | 24.6°C | 4.4°C | 34 mm | 77% | 3.3 m/s | 3.4 |
| 2017 | 18.4°C | 13.8°C | 9.2°C | 22.4°C | 5.0°C | 58 mm | 83% | 3.2 m/s | 2.9 |
| 2016 | 21.3°C | 16.5°C | 11.7°C | 28.8°C | 5.8°C | 38 mm | 83% | 3.1 m/s | 3 |
| 2015 | 17.5°C | 12.8°C | 8.1°C | 20.3°C | 5.3°C | 49 mm | 82% | 2.9 m/s | 3.4 |
| 2014 | 20.6°C | 15.5°C | 10.4°C | 23.6°C | 5.9°C | 17 mm | 83% | 2.1 m/s | 3.2 |
| 2013 | 18.7°C | 14.0°C | 9.3°C | 26.9°C | 5.7°C | 41 mm | 83% | 2.7 m/s | 2.9 |
| 2012 | 18.4°C | 13.4°C | 8.4°C | 26.1°C | 5.0°C | 53 mm | 81% | 3.3 m/s | 3.5 |
| 2011 | 20.8°C | 15.9°C | 11.0°C | 27.1°C | 7.6°C | 32 mm | 80% | 3.7 m/s | 3.3 |
| 2010 | 18.3°C | 13.9°C | 9.5°C | 23.0°C | 4.4°C | 61 mm | 83% | 3.3 m/s | 3 |
| 2009 | 19.6°C | 14.9°C | 10.2°C | 24.0°C | 7.0°C | 21 mm | 80% | 3.3 m/s | 3.4 |
| 2008 | 18.2°C | 13.9°C | 9.6°C | 21.9°C | 6.6°C | 58 mm | 82% | 3.1 m/s | 2.9 |
| 2007 | 18.8°C | 14.2°C | 9.5°C | 23.3°C | 5.2°C | 29 mm | 82% | 3.3 m/s | 3.3 |
| 2006 | 22.2°C | 17.5°C | 12.7°C | 26.8°C | 7.7°C | 70 mm | 82% | 3.1 m/s | 3.4 |
| 2005 | 20.9°C | 15.9°C | 10.8°C | 26.4°C | 4.5°C | 56 mm | 81% | 2.9 m/s | 3.3 |
| 2004 | 19.5°C | 14.8°C | 10.1°C | 25.7°C | 5.3°C | 30 mm | 82% | 3.8 m/s | 3.4 |
| 2003 | 20.0°C | 14.4°C | 8.8°C | 25.1°C | 2.5°C | 21 mm | 79% | 2.2 m/s | 3.5 |
| 2002 | 18.8°C | 14.3°C | 9.7°C | 22.4°C | 6.4°C | 37 mm | 83% | 2.6 m/s | 3.3 |
| 2001 | 17.0°C | 13.1°C | 9.1°C | 21.3°C | 7.0°C | 74 mm | 85% | 3.7 m/s | 2.8 |
| 2000 🌧️ | 19.3°C | 15.0°C | 10.8°C | 25.4°C | 6.1°C | 102 mm | 86% | 3.2 m/s | 2.6 |
| 1999 | 20.5°C | 16.0°C | 11.5°C | 27.1°C | 8.6°C | 84 mm | 84% | 3.1 m/s | 3.2 |
| 1998 | 19.3°C | 15.1°C | 10.8°C | 22.5°C | 6.4°C | 97 mm | 84% | 3.3 m/s | 3.1 |
| 1997 | 19.5°C | 14.8°C | 10.0°C | 22.7°C | 6.5°C | 19 mm | 80% | 3 m/s | 3.4 |
| 1996 | 18.2°C | 13.8°C | 9.3°C | 22.7°C | 6.8°C | 23 mm | 79% | 3.5 m/s | 3.1 |
| 1995 | 18.0°C | 13.6°C | 9.2°C | 20.8°C | 4.5°C | 101 mm | 82% | 3.2 m/s | 3 |
| 1994 | 17.0°C | 12.9°C | 8.9°C | 20.4°C | 5.4°C | 85 mm | 84% | 3.5 m/s | 2.9 |
| 1993 | 16.8°C | 12.6°C | 8.5°C | 21.5°C | 5.6°C | 88 mm | 84% | 3.2 m/s | 2.7 |
| 1992 | 18.4°C | 13.7°C | 9.0°C | 23.0°C | 4.8°C | 89 mm | 83% | 3.3 m/s | 3.1 |
| 1991 | 21.2°C | 15.5°C | 9.9°C | 28.1°C | 5.4°C | 46 mm | 75% | 2.9 m/s | 3.6 |
| 1990 | 18.5°C | 13.7°C | 8.8°C | 25.5°C | 4.6°C | 35 mm | 74% | 3.2 m/s | 3.1 |
| 1989 | 20.1°C | 15.6°C | 11.2°C | 25.1°C | 7.1°C | 31 mm | 79% | 3.2 m/s | 3 |
| 1988 | 17.9°C | 13.6°C | 9.3°C | 23.5°C | 3.6°C | 49 mm | 82% | 3.7 m/s | 2.8 |
| 1987 | 18.4°C | 13.8°C | 9.2°C | 23.6°C | 2.8°C | 38 mm | 83% | 3.1 m/s | 3 |
| 1986 ❄️ | 16.6°C | 11.6°C | 6.6°C | 20.9°C | 3.4°C | 29 mm | 81% | 2.6 m/s | 3.4 |
| 1985 | 19.5°C | 14.7°C | 9.9°C | 25.3°C | 5.2°C | 20 mm | 83% | 3.1 m/s | 3.3 |
| 1984 | 18.0°C | 13.6°C | 9.3°C | 24.9°C | 6.2°C | 76 mm | 81% | 3.6 m/s | 2.9 |
| 1983 | 18.2°C | 13.8°C | 9.4°C | 23.4°C | 4.9°C | 62 mm | 83% | 4 m/s | — |
| 1982 | 19.8°C | 14.8°C | 9.7°C | 25.8°C | 5.6°C | 53 mm | 83% | 2.9 m/s | — |
| 1981 | 19.2°C | 14.7°C | 10.3°C | 24.6°C | 6.9°C | 85 mm | 82% | 3.3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 19.3°C with lows near 9.9°C (mean 14.6°C), based on 45 years of NASA POWER data.
September averages 53 mm of rainfall in Stevenage, about average for rainfall. The wettest on record was 102 mm in 2000.
The hottest September reached 30.8°C in 2023. The coldest dipped to 2.5°C in 2003.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.7°C. Daytime highs moved from 18.9°C to 20.8°C and overnight lows from 9.7°C to 11.1°C over the same span.
September is one of the warmer months of the year in Stevenage and about average for rainfall, so plan for around 19.3°C daytime highs and 9.9°C at night.
Not quite — September is the 9th coolest month in Stevenage, averaging 14.6°C.
For September in Stevenage, pack light layers you can adjust through the day, with typical highs of 19.3°C and lows of 9.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 81% — quite humid.
Average wind speed in September is 3.2 m/s. The windiest September on record averaged 4 m/s (1983).
The wettest September on record was 2000 with 102 mm. On average, September sees 53 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 Stevenage 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.
