Westport Island, Maine climate: Climate normals at a NOAA weather station
Westport Island's normal year runs from 14°F January nights to 76°F July afternoons, with 51.7 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.8°C, January lows of −10°C, July highs of 25°C, 1,314 mm of precipitation a year.
- NOAA stationWestport Island
- Station IDUSC00179547
- Location43.89°N 69.71°W
- Elevation90 ft (27 m)
On October 22, the normal high in Westport Island is 56°F and the normal low 40°F, and the chance of measurable rain or snow is 43%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Westport Island.
- Jan 31° 14°
- Feb 33° 16°
- Mar 41° 24°
- Apr 51° 34°
- May 63° 44°
- Jun 70° 53°
- Jul 76° 59°
- Aug 76° 59°
- Sep 69° 51°
- Oct 58° 42°
- Nov 47° 32°
- Dec 37° 22°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like at Westport Island each month?
July is the warmest month, with normal highs of 76°F; January the coldest, with normal lows of 14°F. The most precipitation falls in December (5.39 in), the least in August (3.24 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 31°F | 14°F | 22.7°F | 4.37 | 13 | <1 | 30 | 9 h 10 min |
| February | 33°F | 16°F | 24.6°F | 3.91 | 10 | <1 | 28 | 10 h 30 min |
| March | 41°F | 24°F | 32.4°F | 4.92 | 11 | <1 | 26 | 11 h 50 min |
| April | 51°F | 34°F | 42.9°F | 4.33 | 12 | <1 | 13 | 13 h 20 min |
| May | 63°F | 44°F | 53.3°F | 3.60 | 15 | <1 | 1 | 14 h 40 min |
| June | 70°F | 53°F | 61.7°F | 4.43 | 16 | <1 | <1 | 15 h 30 min |
| July | 76°F | 59°F | 67.8°F | 3.69 | 12 | <1 | <1 | 15 h 10 min |
| August | 76°F | 59°F | 67.2°F | 3.24 | 12 | <1 | <1 | 14 h |
| September | 69°F | 51°F | 60.3°F | 4.32 | 9 | <1 | <1 | 12 h 40 min |
| October | 58°F | 42°F | 49.7°F | 5.17 | 14 | <1 | 5 | 11 h 10 min |
| November | 47°F | 32°F | 39.8°F | 4.35 | 13 | <1 | 18 | 9 h 40 min |
| December | 37°F | 22°F | 29.3°F | 5.39 | 13 | <1 | 28 | 9 h |
| Year (annual) | 54°F | 38°F | 46.0°F | 51.72 | 148 | 1 | 148 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −10°C | −5.2°C | 111 mm |
| February | 1°C | −9°C | −4.1°C | 99 mm |
| March | 5°C | −4°C | 0.2°C | 125 mm |
| April | 11°C | 1°C | 6.1°C | 110 mm |
| May | 17°C | 7°C | 11.8°C | 91 mm |
| June | 21°C | 12°C | 16.5°C | 113 mm |
| July | 25°C | 15°C | 19.9°C | 94 mm |
| August | 24°C | 15°C | 19.6°C | 82 mm |
| September | 21°C | 11°C | 15.7°C | 110 mm |
| October | 14°C | 5°C | 9.8°C | 131 mm |
| November | 8°C | 0°C | 4.3°C | 110 mm |
| December | 3°C | −6°C | −1.5°C | 137 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Bath (8 miles away), gets 72 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00179547; 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.
Which months are mildest at Westport Island?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, September has the fewest days with rain (9).
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 USC00179547.
When is the last frost at Westport Island?
In Westport Island, the last spring frost (32°F) comes after April 28 in half of years and after May 9 in one year in ten; the first autumn frost comes before October 21 in half of years and before October 5 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 9; 9 in 10 after April 16
- First autumn frost, half of years before
- October 211 year in 10 before October 5; 9 in 10 before November 4
NOAA puts the median frost-free season at 175 days, and the season without a hard freeze (28°F) at 203 days.
A hard freeze (28°F) comes after April 13 in half of springs and before November 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Westport Island in zone 6a in ZIP code 04571, the nearest ZIP area.
Frost dates for every NOAA station in Maine · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00179547; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 at Westport Island?
In a normal year in Westport Island, 1 day a year reaches 90°F, 148 nights fall to 32°F or colder and 148 days bring measurable precipitation.
- Days at 90°F or more
- 1a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 148a normal year
- Days that stay below freezing
- 47high of 32°F or less
- Days with 0.01 inch of precipitation
- 148a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00179547.
How sunny is it at Westport Island?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds at Westport Island, 3.8 kWh per square metre a day. August is the sunniest month (81%) and December the cloudiest (62%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 64% | 1.6 |
| February | 69% | 2.5 |
| March | 70% | 3.7 |
| April | 70% | 4.8 |
| May | 70% | 5.5 |
| June | 72% | 5.8 |
| July | 79% | 6.0 |
| August | 81% | 5.5 |
| September | 80% | 4.4 |
| October | 71% | 2.8 |
| November | 67% | 1.8 |
| December | 62% | 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 many heating and cooling degree days does Westport Island record?
A normal year at Westport Island brings 7,165 heating degree days, 33% more than the median U.S. place (5,373), and 265 cooling degree days, 71% 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 1,990 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,313 | 0 |
| February | 1,131 | 0 |
| March | 1,011 | 0 |
| April | 665 | 0 |
| May | 367 | 4 |
| June | 131 | 33 |
| July | 24 | 109 |
| August | 27 | 96 |
| September | 163 | 21 |
| October | 473 | 1 |
| November | 756 | 0 |
| December | 1,105 | 0 |
| Year (annual) | 7,165 | 265 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00179547. 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.
How does Westport Island's climate compare?
Westport Island is warmer than 35 of the 42 places with their own NOAA record in Maine, and wetter than 39. Across the 7,247 U.S. stations with normals, its annual mean of 46.0°F is warmer than 23%.
In the Köppen classification computed from these normals, Westport Island 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 Westport Island share this climate record?
Boothbay Harbor has no NOAA station with 1991-2020 normals of its 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.
- Boothbay Harbor, ME2,085 people · 5 mi SE
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 Westport Island's climate
What is the coldest month at Westport Island?
January, with a normal high of 31°F and a normal low of 14°F. The warmest is July (76°F by day, 59°F at night).
Does it snow at Westport Island?
Yes. NOAA publishes no 1991-2020 snowfall normal for the station; the nearest record that keeps one, Bath (8 miles away), records 72 inches of snow in a normal year.
What is the rainiest month at Westport Island?
December, with 5.39 in of precipitation in a normal year; the driest is August with 3.24 in.
What plant hardiness zone is Westport Island in?
The USDA's 2023 map puts Westport Island in zone 6a in ZIP code 04571, the nearest ZIP area.
How late can frost come at Westport Island?
In half of years the last 32°F night comes after April 28; in one year in ten it comes after May 9. Waiting until May 9 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Maine climateThe statewide normals and every place in the state
- Wiscasset, ME5 miles from this station, 45.9°F a year
- Bath, ME8 miles from this station, 44.6°F a year
- Brunswick, ME11 miles from this station, 45.7°F a year
- Newcastle, ME14 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