Groton weather in September: Groton, Connecticut: normal highs, lows, rain and records for September
Groton in September has a normal high of 74°F and a normal low of 57°F, a daily mean of 65°F, falling from 78°F on the 1st to 69°F by the 30th. Measurable precipitation falls on 9 days in a normal September, 3.83 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 23°C and low of 14°C, 97 mm of precipitation in September.
- NOAA stationGroton New London Airport
- Station IDUSW00014707
- Location41.33°N 72.05°W
- Elevation10 ft (3 m)
- Population10,160
- Jan 38° 23°
- Feb 40° 25°
- Mar 47° 31°
- Apr 56° 39°
- May 65° 49°
- Jun 74° 58°
- Jul 80° 65°
- Aug 79° 64°
- Sep 74° 57°
- Oct 63° 46°
- Nov 53° 37°
- Dec 44° 29°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Groton in September?
The normal high is 74°F and the normal low 57°F, for a daily mean of 65.2°F. September is 6.3°F cooler than August and 10.8°F warmer than October. September is the 4th warmest month of the year in Groton and the wettest. Across the month the normal high falls 9°F, from 78°F on September 1 to 69°F on September 30. From one year to the next September's mean temperature typically moves about 1.7°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 64°F and 67°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 31%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 78°F | 61°F | 29% | 15% |
| September 8 | 76°F | 60°F | 29% | 15% |
| September 15 | 74°F | 57°F | 29% | 15% |
| September 22 | 72°F | 55°F | 30% | 16% |
| September 30 | 69°F | 52°F | 31% | 16% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 78°F | 61°F | 29% | 15% | 13 h 10 min |
| September 2 | 77°F | 61°F | 29% | 15% | 13 h 10 min |
| September 3 | 77°F | 61°F | 29% | 15% | 13 h |
| September 4 | 77°F | 61°F | 29% | 15% | 13 h |
| September 5 | 77°F | 60°F | 29% | 15% | 13 h |
| September 6 | 76°F | 60°F | 29% | 15% | 13 h |
| September 7 | 76°F | 60°F | 29% | 15% | 12 h 50 min |
| September 8 | 76°F | 60°F | 29% | 15% | 12 h 50 min |
| September 9 | 76°F | 59°F | 29% | 15% | 12 h 50 min |
| September 10 | 75°F | 59°F | 29% | 15% | 12 h 50 min |
| September 11 | 75°F | 59°F | 29% | 15% | 12 h 40 min |
| September 12 | 75°F | 58°F | 29% | 15% | 12 h 40 min |
| September 13 | 75°F | 58°F | 29% | 15% | 12 h 40 min |
| September 14 | 74°F | 58°F | 29% | 15% | 12 h 40 min |
| September 15 | 74°F | 57°F | 29% | 15% | 12 h 30 min |
| September 16 | 74°F | 57°F | 29% | 15% | 12 h 30 min |
| September 17 | 73°F | 57°F | 29% | 16% | 12 h 30 min |
| September 18 | 73°F | 56°F | 29% | 16% | 12 h 20 min |
| September 19 | 73°F | 56°F | 30% | 16% | 12 h 20 min |
| September 20 | 72°F | 56°F | 30% | 16% | 12 h 20 min |
| September 21 | 72°F | 55°F | 30% | 16% | 12 h 20 min |
| September 22 | 72°F | 55°F | 30% | 16% | 12 h 10 min |
| September 23 | 71°F | 54°F | 30% | 16% | 12 h 10 min |
| September 24 | 71°F | 54°F | 30% | 16% | 12 h 10 min |
| September 25 | 71°F | 54°F | 30% | 16% | 12 h 10 min |
| September 26 | 70°F | 53°F | 31% | 16% | 12 h |
| September 27 | 70°F | 53°F | 31% | 16% | 12 h |
| September 28 | 69°F | 53°F | 31% | 16% | 12 h |
| September 29 | 69°F | 52°F | 31% | 16% | 11 h 50 min |
| September 30 | 69°F | 52°F | 31% | 16% | 11 h 50 min |
- Normal high
- 74°FSeptember average
- Normal low
- 57°FSeptember average
- Precipitation
- 3.83 inmonth total
- Days with precipitation
- 90.01 inch or more
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 23
- Days at 80°F or more
- 4
- Sunshine
- 78%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00014707; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Groton in September?
On a given September day the chance of 0.01 inch or more is 29% on average, highest around September 30 (31%). In all, 3.83 in falls on 9 days of a normal September, 1 of them with an inch or more.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00014707.
What are the records for September in Groton?
The warmest September temperature on this station's record (since 1999) is 90°F, on September 4, 2018; the coldest is 36°F, on September 29, 2000. The wettest September brought 7.26 in (2008).
The September mean against the 1991-2020 normal of 65.2°F: 2021 67.1°F (+1.9), 2022 66.9°F (+1.7), 2023 67.8°F (+2.6), 2024 63.9°F (−1.4), 2025 62.5°F (−2.7), 2026 64.5°F (−0.7). 3 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 67.1°F | +1.9°F | 6.02 in |
| 2022 | 66.9°F | +1.7°F | 6.09 in |
| 2023 | 67.8°F | +2.6°F | – |
| 2024 | 63.9°F | −1.4°F | 0.73 in |
| 2025 | 62.5°F | −2.7°F | – |
| 2026 | 64.5°F | −0.7°F | 3.74 in |
Source: records: ACIS, station USW00014707; recent months: ACIS, station USW00014707. Records and recent months use complete months only.
How does September in Groton compare across Connecticut?
Across the 13 places PlainClimate covers in Connecticut, September normal highs run from 69°F in Norfolk to 76°F in Hartford; Groton's is 74°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.