September is one of the warmer months of the year in Sleaford, with average highs near 18.4°C and lows around 9.5°C (mean 14°C). It is about average for rainfall, averaging 57 mm of rainfall and 83% relative humidity across the period.
September is one of the warmer months of the year in Sleaford. Across 45 years of records, the warmest September in Sleaford was 2023 — when the month averaged 16.9°C — while the coldest was 1986 at 11.4°C. Typical September days reach 18.4°C with nights near 9.5°C. The long-term trend is warming, about 0.3°C per decade.
September is about average for rainfall in Sleaford, averaging 57 mm of rainfall. The wettest September on record was 2000 with 134 mm, while the driest was 2014 at 15 mm.
Relative humidity in Sleaford during September averages 83%. The most humid September was 2000 at 87%, and the least humid was 1991 at 77%.
September receives about 3.1 kWh/m²/day of solar energy in Sleaford. The sunniest September was 1991 at 3.6 kWh/m²/day, and the cloudiest were 2000 and 2001 at 2.5.
Average wind speed in Sleaford during September is 3.3 m/s. The windiest September was 1983 at 4.2 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 | 13.5°C | 13.6°C | 14.2°C | 13.9°C | 15.0°C | +1.5°C |
| Avg High | 17.8°C | 18.0°C | 18.6°C | 18.6°C | 19.6°C | +1.8°C |
| Avg Low | 9.0°C | 9.3°C | 9.8°C | 9.3°C | 10.4°C | +1.4°C |
| Avg Rain | 54 mm | 64 mm | 58 mm | 52 mm | 59 mm | +5 mm |
September temperatures in Sleaford have risen by about 1.4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 2.3°C (1986) to a record high of 29.4°C (2023).
Rainfall in September is about average for rainfall, averaging 57 mm, with a wettest year of 134 mm.
One of the best times to visit Sleaford
September is one of the best times to visit Sleaford. Expect days averaging 18.4°C and nights around 9.5°C (mean 14°C) — warmer than Sleaford's yearly average — with moderate rainfall (57 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 | 19.0°C | 14.3°C | 9.7°C | 24.1°C | 4.5°C | 63 mm | 80% | 3.7 m/s | 3.2 |
| 2024 | 18.4°C | 14.2°C | 10.0°C | 24.3°C | 3.3°C | 96 mm | 86% | 3.2 m/s | 2.7 |
| 2023 🔥 | 21.7°C | 16.9°C | 12.1°C | 29.4°C | 7.1°C | 64 mm | 83% | 3 m/s | 3.2 |
| 2022 | 19.0°C | 14.6°C | 10.1°C | 24.0°C | 4.8°C | 46 mm | 81% | 2.8 m/s | 3 |
| 2021 | 20.4°C | 15.8°C | 11.2°C | 27.0°C | 6.2°C | 58 mm | 84% | 2.8 m/s | 3.1 |
| 2020 | 18.8°C | 14.0°C | 9.2°C | 24.9°C | 4.2°C | 30 mm | 82% | 3.4 m/s | 3.4 |
| 2019 | 18.8°C | 14.1°C | 9.3°C | 23.2°C | 5.2°C | 95 mm | 82% | 3.3 m/s | 3.4 |
| 2018 | 18.7°C | 13.9°C | 9.1°C | 23.5°C | 3.5°C | 29 mm | 81% | 3.5 m/s | 3.2 |
| 2017 | 17.7°C | 13.3°C | 9.0°C | 22.0°C | 5.1°C | 77 mm | 85% | 3.4 m/s | 2.9 |
| 2016 | 20.4°C | 15.8°C | 11.3°C | 28.4°C | 6.5°C | 58 mm | 84% | 3.3 m/s | 3 |
| 2015 | 17.3°C | 12.5°C | 7.8°C | 20.4°C | 5.3°C | 36 mm | 83% | 2.7 m/s | 3.3 |
| 2014 | 19.7°C | 14.8°C | 9.9°C | 22.6°C | 5.6°C | 15 mm | 84% | 2.1 m/s | 3 |
| 2013 | 18.0°C | 13.4°C | 8.8°C | 23.7°C | 4.9°C | 29 mm | 84% | 2.9 m/s | 3 |
| 2012 | 17.6°C | 12.9°C | 8.3°C | 25.0°C | 5.0°C | 67 mm | 83% | 3.7 m/s | 3.3 |
| 2011 | 19.6°C | 15.0°C | 10.5°C | 26.3°C | 7.2°C | 32 mm | 81% | 3.9 m/s | 3.2 |
| 2010 | 17.8°C | 13.6°C | 9.4°C | 22.5°C | 4.0°C | 80 mm | 84% | 3.5 m/s | 3 |
| 2009 | 18.5°C | 14.1°C | 9.7°C | 24.1°C | 6.9°C | 20 mm | 83% | 3.4 m/s | 3.2 |
| 2008 | 17.5°C | 13.5°C | 9.4°C | 20.7°C | 6.3°C | 71 mm | 85% | 2.9 m/s | 2.7 |
| 2007 | 18.0°C | 13.7°C | 9.5°C | 22.8°C | 4.5°C | 30 mm | 84% | 3.5 m/s | 3.2 |
| 2006 | 21.1°C | 16.6°C | 12.0°C | 26.0°C | 6.9°C | 73 mm | 84% | 3.2 m/s | 3.3 |
| 2005 | 19.8°C | 15.0°C | 10.3°C | 25.3°C | 4.0°C | 54 mm | 83% | 3.1 m/s | 3.2 |
| 2004 | 18.7°C | 14.3°C | 9.9°C | 25.2°C | 5.8°C | 41 mm | 84% | 4 m/s | 3.3 |
| 2003 | 18.9°C | 13.8°C | 8.6°C | 23.6°C | 3.1°C | 29 mm | 82% | 2.3 m/s | 3.4 |
| 2002 | 18.3°C | 14.0°C | 9.7°C | 21.3°C | 6.5°C | 35 mm | 84% | 2.5 m/s | 3.1 |
| 2001 | 16.8°C | 12.9°C | 8.9°C | 20.6°C | 6.6°C | 87 mm | 85% | 3.9 m/s | 2.5 |
| 2000 🌧️ | 18.6°C | 14.4°C | 10.2°C | 25.2°C | 5.8°C | 134 mm | 87% | 3.2 m/s | 2.5 |
| 1999 | 20.2°C | 15.7°C | 11.1°C | 26.5°C | 8.0°C | 67 mm | 84% | 3.1 m/s | 3.1 |
| 1998 | 18.8°C | 14.6°C | 10.4°C | 22.0°C | 5.4°C | 63 mm | 85% | 3.4 m/s | 2.9 |
| 1997 | 18.1°C | 13.8°C | 9.5°C | 21.7°C | 6.4°C | 21 mm | 83% | 3.2 m/s | 3.2 |
| 1996 | 17.6°C | 13.3°C | 9.0°C | 21.7°C | 5.6°C | 20 mm | 81% | 3.5 m/s | 3 |
| 1995 | 17.5°C | 13.3°C | 9.1°C | 20.2°C | 4.2°C | 84 mm | 83% | 3.2 m/s | 2.9 |
| 1994 | 16.3°C | 12.4°C | 8.5°C | 19.9°C | 5.9°C | 108 mm | 84% | 3.8 m/s | 2.9 |
| 1993 | 16.3°C | 12.3°C | 8.3°C | 22.7°C | 4.6°C | 95 mm | 84% | 3.3 m/s | 2.6 |
| 1992 | 18.0°C | 13.4°C | 8.9°C | 23.3°C | 5.2°C | 90 mm | 82% | 3.5 m/s | 3.1 |
| 1991 | 19.9°C | 14.6°C | 9.2°C | 26.7°C | 4.5°C | 59 mm | 77% | 3.2 m/s | 3.6 |
| 1990 | 17.3°C | 13.0°C | 8.8°C | 23.8°C | 4.6°C | 35 mm | 78% | 3.3 m/s | 2.8 |
| 1989 | 18.9°C | 14.7°C | 10.4°C | 24.4°C | 5.5°C | 36 mm | 82% | 3.1 m/s | 3 |
| 1988 | 17.1°C | 13.0°C | 8.8°C | 24.2°C | 4.2°C | 38 mm | 83% | 3.9 m/s | 2.7 |
| 1987 | 17.6°C | 13.2°C | 8.8°C | 22.9°C | 2.8°C | 45 mm | 83% | 3.3 m/s | 3 |
| 1986 ❄️ | 16.3°C | 11.4°C | 6.5°C | 20.9°C | 2.3°C | 17 mm | 82% | 2.7 m/s | 3.3 |
| 1985 | 18.7°C | 14.1°C | 9.5°C | 23.7°C | 5.7°C | 29 mm | 84% | 3.3 m/s | 3.1 |
| 1984 | 17.2°C | 13.2°C | 9.1°C | 24.0°C | 6.0°C | 90 mm | 82% | 3.7 m/s | 2.7 |
| 1983 | 17.4°C | 13.3°C | 9.1°C | 22.7°C | 4.7°C | 73 mm | 83% | 4.2 m/s | — |
| 1982 | 18.7°C | 14.0°C | 9.3°C | 25.4°C | 5.2°C | 57 mm | 84% | 3.2 m/s | — |
| 1981 | 18.5°C | 14.2°C | 9.9°C | 23.0°C | 6.8°C | 100 mm | 83% | 3.5 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 18.4°C with lows near 9.5°C (mean 14°C), based on 45 years of NASA POWER data.
September averages 57 mm of rainfall in Sleaford, about average for rainfall. The wettest on record was 134 mm in 2000.
The hottest September reached 29.4°C in 2023. The coldest dipped to 2.3°C in 1986.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.4°C. Daytime highs moved from 18.1°C to 19.7°C and overnight lows from 9.4°C to 10.6°C over the same span.
September is one of the warmer months of the year in Sleaford and about average for rainfall, so plan for around 18.4°C daytime highs and 9.5°C at night.
Not quite — September is the 9th coolest month in Sleaford, averaging 14°C.
For September in Sleaford, pack light layers you can adjust through the day, with typical highs of 18.4°C and lows of 9.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 83% — quite humid.
Average wind speed in September is 3.3 m/s. The windiest September on record averaged 4.2 m/s (1983).
The wettest September on record was 2000 with 134 mm. On average, September sees 57 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 Sleaford 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.
