Groton weather in December: Groton, Connecticut: normal highs, lows, rain and records for December
Groton in December has a normal high of 44°F and a normal low of 29°F, a daily mean of 37°F, falling from 48°F on the 1st to 40°F by the 31st. Measurable precipitation falls on 10 days in a normal December, 3.13 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 7°C and low of −2°C, 80 mm of precipitation in December.
- 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 December?
The normal high is 44°F and the normal low 29°F, for a daily mean of 36.5°F. December is 8.6°F cooler than November and 5.7°F warmer than January. December is the 10th warmest month of the year in Groton and the 10th wettest. Across the month the normal high falls 8°F, from 48°F on December 1 to 40°F on December 31. From one year to the next December's mean temperature typically moves about 3.4°F either way (NOAA's standard deviation), so roughly two Decembers in three average between 33°F and 40°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 33%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| December 1 | 48°F | 33°F | 32% | 20% |
| December 8 | 46°F | 31°F | 33% | 20% |
| December 15 | 44°F | 29°F | 32% | 20% |
| December 22 | 42°F | 27°F | 32% | 19% |
| December 31 | 40°F | 25°F | 32% | 19% |
Every day of December: normal high, low and chance of precipitation (warmest afternoon December 1, coldest night December 31)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| December 1 | 48°F | 33°F | 32% | 20% | 9 h 30 min |
| December 2 | 48°F | 33°F | 32% | 20% | 9 h 30 min |
| December 3 | 48°F | 32°F | 32% | 20% | 9 h 20 min |
| December 4 | 47°F | 32°F | 32% | 20% | 9 h 20 min |
| December 5 | 47°F | 32°F | 32% | 20% | 9 h 20 min |
| December 6 | 47°F | 32°F | 32% | 20% | 9 h 20 min |
| December 7 | 46°F | 31°F | 33% | 20% | 9 h 20 min |
| December 8 | 46°F | 31°F | 33% | 20% | 9 h 20 min |
| December 9 | 46°F | 31°F | 33% | 20% | 9 h 20 min |
| December 10 | 45°F | 31°F | 33% | 20% | 9 h 20 min |
| December 11 | 45°F | 30°F | 33% | 20% | 9 h 20 min |
| December 12 | 45°F | 30°F | 32% | 20% | 9 h 10 min |
| December 13 | 45°F | 30°F | 32% | 20% | 9 h 10 min |
| December 14 | 44°F | 30°F | 32% | 20% | 9 h 10 min |
| December 15 | 44°F | 29°F | 32% | 20% | 9 h 10 min |
| December 16 | 44°F | 29°F | 32% | 20% | 9 h 10 min |
| December 17 | 44°F | 29°F | 32% | 20% | 9 h 10 min |
| December 18 | 43°F | 28°F | 32% | 20% | 9 h 10 min |
| December 19 | 43°F | 28°F | 32% | 19% | 9 h 10 min |
| December 20 | 43°F | 28°F | 32% | 19% | 9 h 10 min |
| December 21 | 42°F | 28°F | 32% | 19% | 9 h 10 min |
| December 22 | 42°F | 27°F | 32% | 19% | 9 h 10 min |
| December 23 | 42°F | 27°F | 32% | 19% | 9 h 10 min |
| December 24 | 42°F | 27°F | 32% | 19% | 9 h 10 min |
| December 25 | 42°F | 27°F | 32% | 19% | 9 h 10 min |
| December 26 | 41°F | 26°F | 32% | 19% | 9 h 10 min |
| December 27 | 41°F | 26°F | 32% | 19% | 9 h 10 min |
| December 28 | 41°F | 26°F | 32% | 19% | 9 h 10 min |
| December 29 | 41°F | 26°F | 32% | 19% | 9 h 10 min |
| December 30 | 40°F | 26°F | 32% | 19% | 9 h 10 min |
| December 31 | 40°F | 25°F | 32% | 19% | 9 h 10 min |
- Normal high
- 44°FDecember average
- Normal low
- 29°FDecember average
- Precipitation
- 3.13 inmonth total
- Days with precipitation
- 100.01 inch or more
- Nights at 32°F or colder
- 22
- Daylight
- 9 h 30 min to 9 h 10 minDecember 1 to December 31
- Sunshine
- 67%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 December?
On a given December day the chance of 0.01 inch or more is 32% on average, highest around December 7 (33%). In all, 3.13 in falls on 10 days of a normal December, 1 of them with an inch or more.
In a normal December in Groton, 22 nights fall to freezing and 3 days stay below freezing all day.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00014707.
What are the records for December in Groton?
The warmest December temperature on this station's record (since 1999) is 66°F, on December 1, 2001; the coldest is 6°F, on December 21, 2004. The wettest December brought 7.04 in (2023).
The December mean against the 1991-2020 normal of 36.5°F: 2021 39.1°F (+2.6), 2022 37.9°F (+1.4), 2023 41.8°F (+5.3), 2024 34.2°F (−2.3), 2025 31.4°F (−5.1). 3 of 5 ran warmer than normal.
| December | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 39.1°F | +2.6°F | 1.20 in |
| 2022 | 37.9°F | +1.4°F | 4.90 in |
| 2023 | 41.8°F | +5.3°F | 7.04 in |
| 2024 | 34.2°F | −2.3°F | 5.64 in |
| 2025 | 31.4°F | −5.1°F | 1.99 in |
Source: records: ACIS, station USW00014707; recent months: ACIS, station USW00014707. Records and recent months use complete months only.
How does December in Groton compare across Connecticut?
Across the 13 places PlainClimate covers in Connecticut, December normal highs run from 35°F in Norfolk to 44°F in Groton; Groton's is 44°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.