September is one of the warmer months of the year in Norwalk, with average highs near 23°C and lows around 16.4°C (mean 19.7°C). It is about average for rainfall, averaging 101 mm of rainfall and 76% relative humidity across the period.
September is one of the warmer months of the year in Norwalk. Across 45 years of records, the warmest September in Norwalk was 2015 — when the month averaged 21.9°C — while the coldest was 1984 at 17.2°C. Typical September days reach 23°C with nights near 16.4°C. The long-term trend is warming, about 0.6°C per decade.
September is about average for rainfall in Norwalk, averaging 101 mm of rainfall. The wettest September on record was 2023 with 232 mm, while the driest was 2024 at 20 mm.
Relative humidity in Norwalk during September averages 76%. The most humid September was 2011 at 86%, and the least humid was 1983 at 67%.
September receives about 4.3 kWh/m²/day of solar energy in Norwalk. The sunniest Septembers were 1984 and 2007 at 4.9 kWh/m²/day, and the cloudiest was 2018 at 3.3.
Average wind speed in Norwalk during September is 2.5 m/s. The windiest Septembers were 1981 and 2010 at 2.8 m/s, while the calmest was 1982 at 2.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 18.8°C | 19.0°C | 19.8°C | 20.6°C | 20.5°C | +1.7°C |
| Avg High | 22.4°C | 22.3°C | 23.1°C | 23.8°C | 23.7°C | +1.3°C |
| Avg Low | 15.2°C | 15.8°C | 16.5°C | 17.3°C | 17.3°C | +2.1°C |
| Avg Rain | 82 mm | 108 mm | 109 mm | 94 mm | 112 mm | +30 mm |
September temperatures in Norwalk have risen by about 1.7°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 7.4°C (2000) to a record high of 32.6°C (2023).
Rainfall in September is about average for rainfall, averaging 101 mm, with a wettest year of 232 mm.
One of the best times to visit Norwalk
September is one of the best times to visit Norwalk. Expect days averaging 23°C and nights around 16.4°C (mean 19.7°C) — warmer than Norwalk's yearly average — with higher rainfall (101 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 | 24.5°C | 21.1°C | 17.6°C | 27.8°C | 14.6°C | 64 mm | 74% | 2.2 m/s | 4.5 |
| 2024 | 23.3°C | 20.0°C | 16.7°C | 27.0°C | 13.8°C | 20 mm | 75% | 2.4 m/s | 4.4 |
| 2023 🌧️ | 23.8°C | 20.7°C | 17.6°C | 32.6°C | 12.0°C | 232 mm | 80% | 2.6 m/s | 3.9 |
| 2022 | 23.7°C | 20.4°C | 17.1°C | 28.0°C | 10.6°C | 125 mm | 74% | 2.6 m/s | 4.3 |
| 2021 | 23.7°C | 20.8°C | 17.9°C | 27.5°C | 13.2°C | 168 mm | 80% | 2.7 m/s | 4.3 |
| 2020 | 23.4°C | 20.1°C | 16.9°C | 28.2°C | 10.8°C | 67 mm | 75% | 2.6 m/s | 4.4 |
| 2019 | 23.9°C | 20.4°C | 16.8°C | 27.0°C | 11.8°C | 38 mm | 74% | 2.4 m/s | 4.5 |
| 2018 | 23.8°C | 21.3°C | 18.7°C | 32.1°C | 12.7°C | 190 mm | 84% | 2.4 m/s | 3.3 |
| 2017 | 23.9°C | 20.5°C | 17.1°C | 29.9°C | 12.2°C | 64 mm | 77% | 2.4 m/s | 4.4 |
| 2016 | 24.6°C | 21.3°C | 18.1°C | 30.2°C | 12.7°C | 67 mm | 73% | 2.7 m/s | 4.4 |
| 2015 🔥 | 25.6°C | 21.9°C | 18.1°C | 30.9°C | 13.0°C | 97 mm | 75% | 2.3 m/s | 4.7 |
| 2014 | 23.7°C | 20.3°C | 16.8°C | 29.7°C | 11.8°C | 41 mm | 72% | 2.3 m/s | 4.5 |
| 2013 | 22.7°C | 18.9°C | 15.1°C | 29.1°C | 9.9°C | 57 mm | 72% | 2.4 m/s | 4.6 |
| 2012 | 23.1°C | 20.1°C | 17.1°C | 29.5°C | 12.7°C | 117 mm | 75% | 2.6 m/s | 4.2 |
| 2011 | 22.8°C | 20.2°C | 17.6°C | 25.8°C | 11.1°C | 179 mm | 86% | 2.4 m/s | 3.8 |
| 2010 | 24.3°C | 20.9°C | 17.6°C | 31.6°C | 13.2°C | 91 mm | 74% | 2.8 m/s | 4.3 |
| 2009 | 22.2°C | 18.9°C | 15.7°C | 27.9°C | 11.0°C | 62 mm | 75% | 2.5 m/s | 4.3 |
| 2008 | 22.9°C | 19.8°C | 16.8°C | 28.6°C | 12.1°C | 196 mm | 79% | 2.4 m/s | 4.4 |
| 2007 | 24.1°C | 20.5°C | 16.9°C | 27.2°C | 12.0°C | 37 mm | 73% | 2.4 m/s | 4.9 |
| 2006 | 21.7°C | 18.8°C | 15.9°C | 25.3°C | 11.5°C | 88 mm | 79% | 2.6 m/s | 3.9 |
| 2005 | 25.6°C | 21.8°C | 18.0°C | 30.7°C | 11.8°C | 45 mm | 69% | 2.3 m/s | 4.8 |
| 2004 | 23.4°C | 20.2°C | 17.1°C | 27.8°C | 11.5°C | 197 mm | 80% | 2.4 m/s | 4.1 |
| 2003 | 22.5°C | 19.7°C | 16.9°C | 25.6°C | 11.1°C | 134 mm | 81% | 2.6 m/s | 3.8 |
| 2002 | 23.5°C | 20.2°C | 16.9°C | 30.3°C | 12.8°C | 128 mm | 77% | 2.5 m/s | 4.5 |
| 2001 | 22.9°C | 19.4°C | 15.9°C | 26.7°C | 11.2°C | 92 mm | 73% | 2.5 m/s | 4.6 |
| 2000 | 22.0°C | 18.5°C | 15.1°C | 27.7°C | 7.4°C | 111 mm | 76% | 2.5 m/s | 4.2 |
| 1999 | 22.8°C | 19.9°C | 16.9°C | 26.9°C | 11.0°C | 201 mm | 80% | 2.6 m/s | 4.1 |
| 1998 | 23.9°C | 20.2°C | 16.5°C | 28.4°C | 10.9°C | 70 mm | 73% | 2.4 m/s | 4.4 |
| 1997 | 22.4°C | 18.8°C | 15.3°C | 26.5°C | 10.1°C | 39 mm | 74% | 2.7 m/s | 4.5 |
| 1996 | 22.2°C | 19.2°C | 16.3°C | 29.2°C | 11.0°C | 146 mm | 80% | 2.6 m/s | 3.6 |
| 1995 | 22.5°C | 19.0°C | 15.6°C | 27.5°C | 10.5°C | 101 mm | 69% | 2.7 m/s | 4.3 |
| 1994 | 21.8°C | 18.3°C | 14.9°C | 26.2°C | 11.8°C | 100 mm | 75% | 2.7 m/s | 4.3 |
| 1993 | 22.3°C | 19.2°C | 16.1°C | 29.1°C | 9.8°C | 136 mm | 77% | 2.6 m/s | 3.4 |
| 1992 | 21.4°C | 18.4°C | 15.3°C | 25.3°C | 7.8°C | 103 mm | 78% | 2.7 m/s | 4 |
| 1991 | 21.9°C | 18.6°C | 15.3°C | 29.3°C | 7.6°C | 120 mm | 72% | 2.6 m/s | 4.3 |
| 1990 | 22.0°C | 18.7°C | 15.4°C | 27.1°C | 9.0°C | 68 mm | 76% | 2.5 m/s | 4.4 |
| 1989 | 22.4°C | 19.1°C | 15.8°C | 30.1°C | 9.0°C | 121 mm | 78% | 2.6 m/s | 4.1 |
| 1988 | 22.1°C | 18.3°C | 14.5°C | 25.5°C | 10.3°C | 78 mm | 72% | 2.4 m/s | 4.7 |
| 1987 | 21.7°C | 18.7°C | 15.6°C | 25.6°C | 10.4°C | 134 mm | 81% | 2.5 m/s | 3.8 |
| 1986 | 22.1°C | 18.6°C | 15.1°C | 26.9°C | 9.4°C | 36 mm | 73% | 2.5 m/s | 4 |
| 1985 | 23.3°C | 19.7°C | 16.0°C | 29.5°C | 11.0°C | 84 mm | 73% | 2.4 m/s | 4.4 |
| 1984 ❄️ | 20.9°C | 17.2°C | 13.6°C | 26.2°C | 7.8°C | 64 mm | 73% | 2.3 m/s | 4.9 |
| 1983 | 24.6°C | 20.4°C | 16.2°C | 30.6°C | 10.1°C | 71 mm | 67% | 2.2 m/s | — |
| 1982 | 22.6°C | 18.7°C | 14.8°C | 28.5°C | 12.2°C | 47 mm | 73% | 2.1 m/s | — |
| 1981 | 22.0°C | 18.4°C | 14.8°C | 27.7°C | 8.6°C | 108 mm | 72% | 2.8 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 23°C with lows near 16.4°C (mean 19.7°C), based on 45 years of NASA POWER data.
September averages 101 mm of rainfall in Norwalk, about average for rainfall. The wettest on record was 232 mm in 2023.
The hottest September reached 32.6°C in 2023. The coldest dipped to 7.4°C in 2000.
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 22.7°C to 23.8°C and overnight lows from 15.1°C to 17.4°C over the same span.
September is one of the warmer months of the year in Norwalk and about average for rainfall, so plan for around 23°C daytime highs and 16.4°C at night.
Not quite — September is the 10th coolest month in Norwalk, averaging 19.7°C.
For September in Norwalk, pack light layers you can adjust through the day, with typical highs of 23°C and lows of 16.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 76% — quite humid.
Average wind speed in September is 2.5 m/s. The windiest September on record averaged 2.8 m/s (1981).
The wettest September on record was 2023 with 232 mm. On average, September sees 101 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 Norwalk 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.
