Willimantic, Connecticut climate: Normal weather by month, frost dates and records
Willimantic's normal year runs from 18°F January nights to 83°F July afternoons, with 43.3 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.9°C, January lows of −8°C, July highs of 28°C, 1,099 mm of precipitation a year.
- NOAA stationWillimantic Windham Airport
- Station IDUSW00054767
- Location41.74°N 72.18°W
- Elevation247 ft (75 m)
- From the center2 miles
- Population (census place)17,774
On October 14, the normal high in Willimantic is 63°F and the normal low 41°F, and the chance of measurable rain or snow is 42%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Willimantic.
- Jan 36° 18°
- Feb 39° 19°
- Mar 47° 27°
- Apr 59° 37°
- May 70° 47°
- Jun 78° 56°
- Jul 83° 62°
- Aug 81° 60°
- Sep 74° 52°
- Oct 63° 41°
- Nov 52° 31°
- Dec 41° 24°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Willimantic each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 18°F. The most precipitation falls in August (4.37 in), the least in February (2.66 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 36°F | 18°F | 27.1°F | 3.20 | 10 | <1 | 28 | 9 h 30 min |
| February | 39°F | 19°F | 29.1°F | 2.66 | 10 | <1 | 25 | 10 h 30 min |
| March | 47°F | 27°F | 37.0°F | 3.95 | 11 | <1 | 23 | 11 h 50 min |
| April | 59°F | 37°F | 48.0°F | 3.97 | 12 | <1 | 9 | 13 h 20 min |
| May | 70°F | 47°F | 58.5°F | 3.40 | 14 | 1 | 1 | 14 h 30 min |
| June | 78°F | 56°F | 67.0°F | 3.87 | 13 | 2 | <1 | 15 h 10 min |
| July | 83°F | 62°F | 72.4°F | 2.66 | 13 | 4 | <1 | 15 h |
| August | 81°F | 60°F | 70.6°F | 4.37 | 13 | 3 | <1 | 13 h 50 min |
| September | 74°F | 52°F | 63.3°F | 4.11 | 13 | 1 | <1 | 12 h 30 min |
| October | 63°F | 41°F | 51.8°F | 3.83 | 13 | <1 | 6 | 11 h 10 min |
| November | 52°F | 31°F | 41.5°F | 3.55 | 10 | <1 | 18 | 9 h 50 min |
| December | 41°F | 24°F | 32.6°F | 3.68 | 11 | <1 | 25 | 9 h 10 min |
| Year (annual) | 60°F | 40°F | 49.9°F | 43.25 | 143 | 11 | 135 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 2°C | −8°C | −2.7°C | 81 mm |
| February | 4°C | −7°C | −1.6°C | 68 mm |
| March | 8°C | −3°C | 2.8°C | 100 mm |
| April | 15°C | 3°C | 8.9°C | 101 mm |
| May | 21°C | 8°C | 14.7°C | 86 mm |
| June | 26°C | 13°C | 19.4°C | 98 mm |
| July | 28°C | 17°C | 22.4°C | 68 mm |
| August | 27°C | 16°C | 21.4°C | 111 mm |
| September | 24°C | 11°C | 17.4°C | 104 mm |
| October | 17°C | 5°C | 11.0°C | 97 mm |
| November | 11°C | 0°C | 5.3°C | 90 mm |
| December | 5°C | −5°C | 0.3°C | 93 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Storrs (4 miles away), gets 39 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00054767; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Willimantic?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, August has the fewest days with rain (13).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00054767.
When is the last frost in Willimantic?
In Willimantic, the last spring frost (32°F) comes after April 28 in half of years and after May 11 in one year in ten; the first autumn frost comes before October 13 in half of years and before October 2 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 281 year in 10 after May 11; 9 in 10 after April 17
- First autumn frost, half of years before
- October 131 year in 10 before October 2; 9 in 10 before October 29
NOAA puts the median frost-free season at 167 days, and the season without a hard freeze (28°F) at 193 days.
A hard freeze (28°F) comes after April 14 in half of springs and before October 25 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Willimantic in zone 6b across its 2 ZIP code areas (6b in 06226, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, Willimantic's NOAA station is in zone 6b: the coldest night of a typical year reaches −4°F (22 complete years).
Frost dates for every NOAA station in Connecticut · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00054767; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
What hardiness zone is each Willimantic ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. Willimantic's 2 ZIP code areas are all in zone 6b. Each ZIP's frost dates are in the frost tool.
Source: USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; ZIP areas in the place: Census Bureau 2020 ZCTA-to-place relationship file. A ZIP area counts when at least a tenth of its land (and 0.5 km²) lies in the place.
How hot and how cold does it get in Willimantic?
In a normal year in Willimantic, 11 days a year reach 90°F, 135 nights fall to 32°F or colder and 143 days bring measurable precipitation.
- Days at 90°F or more
- 11a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 135a normal year
- Days that stay below freezing
- 25high of 32°F or less
- Days with 0.01 inch of precipitation
- 143a normal year
The highest temperature in this station's record (since 1996) is 101°F, on August 9, 2001; the lowest is −16°F, on February 21, 2015.
The wettest calendar year on that record is 2011, with 59.67 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00054767; records: ACIS (NOAA Regional Climate Centers), station USW00054767. Records use complete months only; a month missing more than three days is left out.
How sunny is Willimantic?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Willimantic, 3.9 kWh per square metre a day. July is the sunniest month (79%) and December the cloudiest (67%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 70% | 1.9 |
| February | 70% | 2.7 |
| March | 69% | 3.7 |
| April | 71% | 4.9 |
| May | 70% | 5.5 |
| June | 74% | 5.9 |
| July | 79% | 6.0 |
| August | 79% | 5.3 |
| September | 78% | 4.4 |
| October | 71% | 2.9 |
| November | 72% | 2.1 |
| December | 67% | 1.5 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Willimantic need?
A normal year in Willimantic brings 6,094 heating degree days, 13% more than the median U.S. place (5,373), and 626 cooling degree days, 31% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,758 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,173 | 0 |
| February | 1,005 | 0 |
| March | 868 | 0 |
| April | 515 | 4 |
| May | 227 | 24 |
| June | 50 | 110 |
| July | 4 | 232 |
| August | 11 | 186 |
| September | 113 | 63 |
| October | 416 | 6 |
| November | 705 | 0 |
| December | 1,006 | 0 |
| Year (annual) | 6,094 | 626 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00054767. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Willimantic been warmer than normal lately?
2025 averaged 50.0°F, 0.1°F above the 1991-2020 normal of 49.9°F. 5 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 51.4°F | +1.5°F | 40.87 |
| 2022 | 50.9°F | +1.0°F | 34.25 |
| 2023 | 52.1°F | +2.2°F | 55.88 |
| 2024 | 51.7°F | +1.8°F | 41.57 |
| 2025 | 50.0°F | +0.1°F | – |
Source: observed years: ACIS, station USW00054767. A year counts only with all twelve months complete.
How does Willimantic's climate compare?
Willimantic is warmer than 4 of the other 12 places with their own NOAA record in Connecticut, and wetter than 2. Across the 7,247 U.S. stations with normals, its annual mean of 49.9°F is warmer than 40%.
In the Köppen classification computed from these normals, Willimantic is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Willimantic share this climate record?
4 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Colchester, CT15,752 people · 14 mi SW
- South Windham, CT1,391 people · 4 mi S
- Mansfield Center, CT988 people · 2 mi N
- Terramuggus, CT976 people · 17 mi SW
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Willimantic's climate
What is the coldest month in Willimantic?
January, with a normal high of 36°F and a normal low of 18°F. The warmest is July (83°F by day, 62°F at night).
Does it snow in Willimantic?
Yes. NOAA publishes no 1991-2020 snowfall normal for Willimantic's NOAA station; the nearest record that keeps one, Storrs (4 miles away), records 39 inches of snow in a normal year.
What is the rainiest month in Willimantic?
August, with 4.37 in of precipitation in a normal year; the driest is February with 2.66 in.
What plant hardiness zone is Willimantic in?
The USDA's 2023 map puts Willimantic in zone 6b across its 2 ZIP code areas (6b in 06226, the largest). By the same method at Willimantic's NOAA station, the coldest night of a typical year reaches −4°F (22 years, 1991-2020): zone 6b.
How late can frost come in Willimantic?
In half of years the last 32°F night comes after April 28; in one year in ten it comes after May 11. Waiting until May 11 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Connecticut climateThe statewide normals and every place in the state
- Storrs, CT4 miles from this station, 49.6°F a year
- Hampton, CT7 miles from this station, 48.6°F a year
- Norwich, CT16 miles from this station, 51.8°F a year
- Staffordville, CT18 miles from this station, 47.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made