Climate averages 1991–2020
Norwalk weather
in September.
A warm, wet month: the 4th warmest and the joint 7th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Norwalk: daytime highs average 23.1°C and nights cool to about 16.4°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 94 mm of rain on roughly 9 days, which makes September a wet month (the joint 7th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 31 min on an average September day.
The nearest other city in this atlas is Stamford (13 km away). In September its highs average 23.2°C, about as warm as Norwalk, with 94 mm of rain.
Among the 498 cities listed in the United States, Norwalk ranks joint 401st of 498 for the warmest September highs and joint 365th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Norwalk is 3.8°C cooler than that mean.
From September to October, average highs fall by 6.4°C to 16.7°C, and monthly rainfall rises from 94 mm to 100 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Norwalk climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 2.6°C-4.1°C | -4.1°C | 84 | 9.0 | 9.610 h |
| February | 3.8°C-3.8°C | -3.8°C | 78 | 8.7 | 10.611 h |
| March | 7.8°C-0.1°C | -0.1°C | 105 | 10.3 | 11.912 h |
| April | 14.0°C5.5°C | 5.5°C | 93 | 10.5 | 13.313 h |
| May | 19.5°C11.2°C | 11.2°C | 85 | 10.9 | 14.514 h |
| June | 24.8°C16.9°C | 16.9°C | 94 | 10.8 | 15.115 h |
| July | 28.1°C20.5°C | 20.5°C | 92 | 10.7 | 14.815 h |
| August | 27.0°C19.9°C | 19.9°C | 103 | 10.5 | 13.814 h |
| September, selected | 23.1°C16.4°C | 16.4°C | 94 | 9.0 | 12.513 h |
| October | 16.7°C10.5°C | 10.5°C | 100 | 8.5 | 11.111 h |
| November | 10.7°C4.8°C | 4.8°C | 82 | 8.5 | 9.910 h |
| December | 5.5°C-0.2°C | -0.2°C | 105 | 9.8 | 9.39 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Stamford in SeptemberUnited States · 13 kmHigh 23.2°C · Low 16.4°C · 94 mm rain
- Bridgeport in SeptemberUnited States · 20 kmHigh 22.8°C · Low 16.4°C · 103 mm rain
- Danbury in SeptemberUnited States · 31 kmHigh 23.0°C · Low 14.6°C · 108 mm rain
- Greenburgh in SeptemberUnited States · 38 kmHigh 23.3°C · Low 15.9°C · 95 mm rain
- New Haven in SeptemberUnited States · 45 kmHigh 22.6°C · Low 16.2°C · 109 mm rain
- Yonkers in SeptemberUnited States · 46 kmHigh 23.7°C · Low 15.8°C · 101 mm rain
- The Bronx in SeptemberUnited States · 49 kmHigh 23.8°C · Low 15.7°C · 92 mm rain
- Waterbury in SeptemberUnited States · 57 kmHigh 23.2°C · Low 14.6°C · 101 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Norwalk) is explained once on the Norwalk year overview and on the Sources, method and limits page.
Stamford lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.