Belfast, Maine climate: Normal weather by month, frost dates and records
Belfast's normal year runs from 10°F January nights to 77°F July afternoons, with 48.8 inches of precipitation and 72 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.7°C, January lows of −12°C, July highs of 25°C, 1,239 mm of precipitation a year.
- NOAA stationBelfast
- Station IDUSC00170480
- Location44.40°N 68.99°W
- Elevation20 ft (6 m)
- Population6,993
On October 23, the normal high in Belfast is 55°F and the normal low 36°F, and the chance of measurable rain or snow is 31%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Belfast.
- Jan 30° 10°
- Feb 32° 12°
- Mar 40° 20°
- Apr 52° 31°
- May 63° 41°
- Jun 72° 51°
- Jul 77° 57°
- Aug 76° 56°
- Sep 70° 48°
- Oct 57° 38°
- Nov 46° 29°
- Dec 35° 18°
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 Belfast each month?
July is the warmest month, with normal highs of 77°F; January the coldest, with normal lows of 10°F. The most precipitation falls in October (5.38 in), the least in August (3.06 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 30°F | 10°F | 19.8°F | 3.94 | 19.2 | 9 | <1 | 30 | 9 h 10 min |
| February | 32°F | 12°F | 21.9°F | 3.16 | 22.4 | 7 | <1 | 27 | 10 h 30 min |
| March | 40°F | 20°F | 30.1°F | 4.12 | 11.7 | 8 | <1 | 28 | 11 h 50 min |
| April | 52°F | 31°F | 41.3°F | 4.38 | 2.2 | 10 | <1 | 17 | 13 h 20 min |
| May | 63°F | 41°F | 52.1°F | 3.86 | 0.0 | 10 | <1 | 2 | 14 h 50 min |
| June | 72°F | 51°F | 61.0°F | 4.28 | 0.0 | 10 | 1 | <1 | 15 h 30 min |
| July | 77°F | 57°F | 66.8°F | 3.17 | 0.0 | 9 | 1 | <1 | 15 h 10 min |
| August | 76°F | 56°F | 66.0°F | 3.06 | 0.0 | 8 | 1 | <1 | 14 h 10 min |
| September | 70°F | 48°F | 58.8°F | 4.09 | 0.0 | 7 | <1 | 1 | 12 h 40 min |
| October | 57°F | 38°F | 47.7°F | 5.38 | 0.3 | 10 | <1 | 8 | 11 h |
| November | 46°F | 29°F | 37.2°F | 4.69 | 2.5 | 9 | <1 | 20 | 9 h 40 min |
| December | 35°F | 18°F | 26.6°F | 4.65 | 13.2 | 10 | <1 | 29 | 8 h 50 min |
| Year (annual) | 54°F | 34°F | 44.1°F | 48.78 | 71.5 | 105 | 2 | 162 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −1°C | −12°C | −6.8°C | 100 mm | 49 cm |
| February | 0°C | −11°C | −5.6°C | 80 mm | 57 cm |
| March | 4°C | −6°C | −1.1°C | 105 mm | 30 cm |
| April | 11°C | 0°C | 5.2°C | 111 mm | 6 cm |
| May | 17°C | 5°C | 11.2°C | 98 mm | 0 cm |
| June | 22°C | 10°C | 16.1°C | 109 mm | 0 cm |
| July | 25°C | 14°C | 19.3°C | 81 mm | 0 cm |
| August | 25°C | 13°C | 18.9°C | 78 mm | 0 cm |
| September | 21°C | 9°C | 14.9°C | 104 mm | 0 cm |
| October | 14°C | 3°C | 8.7°C | 137 mm | 1 cm |
| November | 8°C | −2°C | 2.9°C | 119 mm | 6 cm |
| December | 2°C | −8°C | −3.0°C | 118 mm | 34 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00170480; 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 Belfast?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, September has the fewest days with rain (7).
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 USC00170480.
When is the last frost in Belfast?
In Belfast, the last spring frost (32°F) comes after May 7 in half of years and after May 21 in one year in ten; the first autumn frost comes before October 5 in half of years and before September 24 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
- May 71 year in 10 after May 21; 9 in 10 after April 28
- First autumn frost, half of years before
- October 51 year in 10 before September 24; 9 in 10 before October 20
NOAA puts the median frost-free season at 151 days, and the season without a hard freeze (28°F) at 174 days.
A hard freeze (28°F) comes after April 27 in half of springs and before October 19 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Belfast in zone 5b in ZIP code 04915. By the map's own method, the average of each year's coldest night over 1991-2020, Belfast's NOAA station is in zone 5b: the coldest night of a typical year reaches −14°F (30 complete years).
Frost dates for every NOAA station in Maine · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00170480; 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.
How hot and how cold does it get in Belfast?
In a normal year in Belfast, 2 days a year reach 90°F, 162 nights fall to 32°F or colder and 105 days bring measurable precipitation.
- Days at 90°F or more
- 2a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 162a normal year
- Days that stay below freezing
- 47high of 32°F or less
- Days with 0.01 inch of precipitation
- 105a normal year
- Days with 1 inch of snow or more
- 18a normal year
The highest temperature in this station's record (since 1901) is 98°F, on July 19, 1946; the lowest is −28°F, on January 14, 1957.
The wettest calendar year on that record is 2005, with 71.15 in; the snowiest season is 2014–15, with 135.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00170480; records: ACIS (NOAA Regional Climate Centers), station USC00170480. Records use complete months only; a month missing more than three days is left out.
How sunny is Belfast?
Over a year 70% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Belfast, 3.7 kWh per square metre a day. September is the sunniest month (77%) and December the cloudiest (61%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 65% | 1.6 |
| February | 67% | 2.4 |
| March | 69% | 3.6 |
| April | 67% | 4.6 |
| May | 67% | 5.3 |
| June | 69% | 5.6 |
| July | 75% | 5.8 |
| August | 77% | 5.2 |
| September | 77% | 4.2 |
| October | 69% | 2.7 |
| November | 65% | 1.7 |
| December | 61% | 1.3 |
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 Belfast need?
A normal year in Belfast brings 7,785 heating degree days, 45% more than the median U.S. place (5,373), and 204 cooling degree days, 78% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 1,802 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,400 | 0 |
| February | 1,205 | 0 |
| March | 1,083 | 0 |
| April | 711 | 0 |
| May | 403 | 3 |
| June | 147 | 27 |
| July | 32 | 88 |
| August | 40 | 69 |
| September | 203 | 17 |
| October | 538 | 0 |
| November | 834 | 0 |
| December | 1,189 | 0 |
| Year (annual) | 7,785 | 204 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00170480. 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 Belfast been warmer than normal lately?
2021 averaged 47.0°F, 2.9°F above the 1991-2020 normal of 44.1°F.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 47.0°F | +2.9°F | 58.29 | 36.1 |
Over 63 complete years from 1946 to 2021, the station's annual mean temperature rose at a fitted 1.6°F per century (+0.09°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00170480; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Belfast's climate compare?
Belfast is warmer than 21 of the other 41 places with their own NOAA record in Maine, and wetter than 29. Across the 7,247 U.S. stations with normals, its annual mean of 44.1°F is warmer than 16%.
In the Köppen classification computed from these normals, Belfast is Dfb: continental, no dry season, warm 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 Belfast share this climate record?
2 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.
- Searsport, ME2,685 people · 7 mi NE
- Castine, ME1,361 people · 9 mi E
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 Belfast's climate
What is the coldest month in Belfast?
January, with a normal high of 30°F and a normal low of 10°F. The warmest is July (77°F by day, 57°F at night).
Does it snow in Belfast?
Yes: 72 inches in a normal year, falling on 20 days with 0.1 inch or more, the most in February (22.4 inches).
What is the rainiest month in Belfast?
October, with 5.38 in of precipitation in a normal year; the driest is August with 3.06 in.
What plant hardiness zone is Belfast in?
The USDA's 2023 map puts Belfast in zone 5b in ZIP code 04915. By the same method at Belfast's NOAA station, the coldest night of a typical year reaches −14°F (30 years, 1991-2020): zone 5b.
How late can frost come in Belfast?
In half of years the last 32°F night comes after May 7; in one year in ten it comes after May 21. Waiting until May 21 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Maine climateThe statewide normals and every place in the state
- West Rockport (1 mi NNW), ME16 miles from this station, 45.5°F a year
- East Surry, ME27 miles from this station, 44.5°F a year
- Bangor, ME29 miles from this station, 45.0°F a year
- Tenants Harbor, ME30 miles from this station, 46.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made