Groton New London, CT Climate: Temperature & Rain by Month
Annual temperature and rainfall from NOAA NCEI's 1991–2020 normals →; comfort score computed by PlainClimate
30-year climate normals (1991-2020) from Groton New London's primary NOAA station, GROTON NEW LONDON AP.
The climate verdict for Groton New London
Groton New London, Connecticut has a mixed annual climate rather than one dominant extreme. Its NOAA normal shows an annual average of 51°F. Its climate comfort score of 68/100 (good) lands mid-pack nationally, exceeding 56% of station-mapped location scores.
- 51°F
- yearly average temperature, NOAA normal
- 68/100
- comfort score, above 56% of station-mapped location scores
- 39.3"
- precipitation, annual total
- 195 days
- frost-free growing season
Groton New London: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USW00014707 · Groton New London, CT 51°F mean · 39.3" precip
TEMP-COOL · RANK-MID · PHOTO-FINISH · PRCP-MID · SWING-MID · COMF-MID · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 51°F
- RANK-MID #3,156
- PHOTO-FINISH ≈ Monument
- PRCP-MID 39.3"
- SWING-MID 42°F
- COMF-MID 68/100
- LOAD-HEAT 5,521 HDD
- STN-1 USW00014707
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Monument, OR (+ 0.1 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every CT station list.
- Hot Tygart Dam, WV 52°F
- Near Monument, OR 52°F
- Near Hyannis Barnsta…, MA 52°F
- Groton New Lond… (this station) 51°F
- Cold Newport State, RI 51°F
Climate Living Index · Groton New London
Groton New London: 64/100 · grade C
Groton New London publishes 4 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 2 missing weights rescale to 100.
PlainClimate-derived for Groton New London, not an official NOAA rating. Rankings still use Comfort Score 68/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Precipitation balance | 39.3 in · 4.3 from 35 in | 84/100 · B |
| Normal heat + freeze calendar | 108 calendar days | 72/100 · B |
| Frost-free season | 195 days/year | 61/100 · C |
| Annual temperature balance | 51.4°F · 16.1° from 67.5°F | 46/100 · D |
Groton New London · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Groton New London is a continental Köppen climate: Dfa
Coldest-month mean 30.8°F and warmest-month mean 72.3°F place this station in continental, no dry season, hot summer climates (Dfa). Class Dfa is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: continental, specifically continental, no dry season, hot summer.
- Köppen code
- Dfa
- Group
- Continental
- Warmest month
- 72.3°F
- Coldest month
- 30.8°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Groton New London sits across the climate record
Three NOAA fields for Groton New London's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 46th percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 56th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- 42nd percentile swing
- Typical seasonal amplitude versus 6,861 complete station-years.
How Groton New London compares across U.S. station-mapped locations
Groton New London's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
68 Top 44% score exceeds 56% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). This entry sits in this band.
- 70–80: 650 station-mapped locations (11%). Above this entry.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|
| January | 38°F (3°C) | 23°F (-5°C) | 31°F (-1°C) | 2.7" | 25.2 | 0.0 |
| February | 40°F (5°C) | 25°F (-4°C) | 32°F (0°C) | 2.2" | 23.6 | 0.0 |
| March | 47°F (8°C) | 31°F (-1°C) | 39°F (4°C) | 3.8" | 19.1 | 0.0 |
| April | 56°F (13°C) | 39°F (4°C) | 48°F (9°C) | 3.6" | 5.2 | 0.0 |
| May | 65°F (18°C) | 49°F (9°C) | 57°F (14°C) | 3.3" | 0.2 | 0.0 |
| June | 74°F (23°C) | 58°F (15°C) | 66°F (19°C) | 3.3" | 0.0 | 0.1 |
| July | 80°F (27°C) | 65°F (18°C) | 72°F (22°C) | 3.2" | 0.0 | 1.0 |
| August | 79°F (26°C) | 64°F (18°C) | 72°F (22°C) | 3.3" | 0.0 | 0.6 |
| September | 74°F (23°C) | 57°F (14°C) | 65°F (18°C) | 3.8" | 0.0 | 0.0 |
| October | 63°F (17°C) | 46°F (8°C) | 54°F (12°C) | 3.7" | 1.9 | 0.0 |
| November | 53°F (12°C) | 37°F (3°C) | 45°F (7°C) | 3.2" | 10.4 | 0.0 |
| December | 44°F (7°C) | 29°F (-2°C) | 37°F (3°C) | 3.1" | 21.7 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 80°F around July 17, short of 90°F on every date, while 108 dates carry a normal low at or below freezing, the coldest 23°F near January 21.
The freezing stretch
The normal low stays at or below 32°F into March 21, then returns to freezing around December 5, covering 108 dates in all.
Derived from the normal daily minimum. This is a different measure from the 50%-probability frost dates shown elsewhere on this page, which come from NOAA’s frost product.
Where the wet dates fall
The likeliest wet date is May 25, when 40% of years recorded at least a hundredth of an inch. The driest is February 1 at 26%. Summed across the calendar, that is about 116 wet dates a year.
The widest day
October 22 carries the biggest normal gap between afternoon and dawn, 18°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Groton New London.
Where Groton New London Stands Nationally
Among the steadiest day-night climates ranked: even the widest normal daily swing holds to roughly 18°F.
Groton New London earns one nationally notable standing (outer quintile) against 6,860 NOAA 1991–2020 normals stations, middle-of-the-pack metrics stay silent here.
Monthly Precipitation
Average monthly rainfall
8.7 days with precipitation
7.9 days with precipitation
9.0 days with precipitation
10.6 days with precipitation
12.4 days with precipitation
10.8 days with precipitation
9.6 days with precipitation
9.5 days with precipitation
8.7 days with precipitation
9.8 days with precipitation
8.9 days with precipitation
10.1 days with precipitation
Groton New London spreads its precipitation across the year
Neither half of the year dominates here: June through August take 25% of the annual total and December through February 20%, with neither reaching the 35% that would mark a distinct wet season. Groton New London has no dry season to plan around, though it does carry a 41.5°F seasonal spread.
The gap between the wettest and driest month still matters: September averages 3.8" and February 2.2". The three wettest months together take 29% of the year, against the 25% a perfectly flat distribution would give them.
Shares are computed from this station's own 1991-2020 monthly precipitation normals. "Spread across the year" means neither the June-August nor the December-February share reaches 35%; it describes an average year, not the variability of any single one.
How Groton New London's precipitation splits across the calendar
About 116 days a year record measurable precipitation here, carrying 39.3" between them, or roughly 0.34 inches on a typical wet day. That sits in the middle band: neither the many-light-days pattern of the Pacific Northwest and the Great Lakes, nor the few-heavy-events pattern of the Gulf and the desert Southwest.
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year and say nothing about the heaviest single storm on record.
Frost Dates & Growing Season
First Fall Freeze
October 28
50% probability date
Last Spring Freeze
April 16
50% probability date
Growing Season
195 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
5,521
Higher = more heating needed
Cooling Degree Days
608
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Nationwide similar cities
Other rankable U.S. places outside CT closest to Groton New London on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (51°F here).
- Aberdeen, WA 51°F · 0.0°F off
- Astoria, OR 51°F · 0.0°F off
- Beatrice, NE 51°F · 0.0°F off
- Brockton, MA 51°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (39.3" here), excluding temperature-peer places.
- Cascade, IA 39.3" · 0.0" off
- Kansas City, MO 39.3" · 0.0" off
- Leon, IA 39.3" · 0.0" off
- Newkirk, OK 39.3" · 0.0" off
Data-derived climate profile
How Groton New London's climate pattern fits together
heating led · moderate · mid swing
Groton New London's energy balance leans toward cold weather: 5,521 annual heating degree days against 608 for cooling. Its 41.5°F seasonal range still makes the monthly rows more useful than the annual average alone.
Groton New London's frost-free season lasts about 195 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
July and January mark the typical warm and cold ends of the calendar in Groton New London's middle-range seasonal profile. The measured spread is 41.5°F. The annual average is 51°F. Neither the annual mean nor one extreme month represents the full calendar on its own.
Groton New London's 39.3 inches of annual precipitation falls in PlainClimate's middle band, so “wet” or “dry” is not the leading description. Snowfall is not added to the interpretation because its annual value is missing. Temperature balance and the calendar distribution carry more information than the annual moisture label alone.
These labels group NOAA 1991-2020 normals from Groton New London's primary station, so the winter figures are a thirty-year average and not a floor: a single hard season can run well below them. Treat each band as a descriptive range for Groton New London, not an official NOAA class or a year-ahead forecast.
Questions about Groton New London's climate
How much rain does Groton New London get? ▼
How cold does Groton New London get in winter? ▼
How much energy does heating and cooling require in Groton New London? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Groton New London's primary station: GROTON NEW LONDON AP (USW00014707). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The conservative exact name-and-state crosswalk finds no Census place match, so PlainClimate treats this as a station-mapped location and does not claim it is a municipality. No exact Gazetteer row for Groton New London; facility counts that depend on place identity are therefore an upper bound, not a municipal census.
On this page every temperature, precipitation, and derived score for Groton New London comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.