Port Alsworth, Alaska climate: Normal weather by month, frost dates and records
Port Alsworth's normal year runs from 5°F January nights to 67°F July afternoons, with 23.6 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 1.6°C, January lows of −15°C, July highs of 19°C, 599 mm of precipitation a year.
- NOAA stationPort Alsworth (1 mi SW)
- Station IDUSW00026562
- Location60.20°N 154.32°W
- Elevation321 ft (98 m)
- From the center3 miles
- Population (census place)174
On October 23, the normal high in Port Alsworth is 38°F and the normal low 22°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Port Alsworth.
- Jan 24° 5°
- Feb 29° 10°
- Mar 32° 11°
- Apr 46° 24°
- May 58° 32°
- Jun 65° 41°
- Jul 67° 46°
- Aug 63° 45°
- Sep 55° 38°
- Oct 42° 25°
- Nov 30° 15°
- Dec 25° 9°
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 Port Alsworth each month?
July is the warmest month, with normal highs of 67°F; January the coldest, with normal lows of 5°F. The most precipitation falls in September (3.48 in), the least in May (0.84 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 24°F | 5°F | 14.3°F | 1.55 | – | <1 | 27 | 6 h 40 min |
| February | 29°F | 10°F | 19.6°F | 1.48 | – | <1 | 25 | 9 h 10 min |
| March | 32°F | 11°F | 21.2°F | 1.17 | – | <1 | 29 | 11 h 40 min |
| April | 46°F | 24°F | 35.0°F | 0.91 | – | <1 | 25 | 14 h 30 min |
| May | 58°F | 32°F | 45.0°F | 0.84 | – | <1 | 16 | 17 h 10 min |
| June | 65°F | 41°F | 53.1°F | 1.24 | – | <1 | 3 | 18 h 50 min |
| July | 67°F | 46°F | 56.6°F | 2.15 | – | <1 | <1 | 18 h 10 min |
| August | 63°F | 45°F | 54.1°F | 3.32 | – | <1 | 1 | 15 h 50 min |
| September | 55°F | 38°F | 46.4°F | 3.48 | – | <1 | 8 | 13 h |
| October | 42°F | 25°F | 33.4°F | 2.25 | – | <1 | 21 | 10 h 20 min |
| November | 30°F | 15°F | 22.4°F | 3.03 | – | <1 | 27 | 7 h 40 min |
| December | 25°F | 9°F | 16.7°F | 2.17 | – | <1 | 28 | 5 h 50 min |
| Year (annual) | 45°F | 25°F | 34.8°F | 23.59 | – | <1 | 209 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −5°C | −15°C | −9.8°C | 39 mm |
| February | −2°C | −12°C | −6.9°C | 38 mm |
| March | 0°C | −12°C | −6.0°C | 30 mm |
| April | 8°C | −4°C | 1.7°C | 23 mm |
| May | 14°C | 0°C | 7.2°C | 21 mm |
| June | 19°C | 5°C | 11.7°C | 31 mm |
| July | 19°C | 8°C | 13.7°C | 55 mm |
| August | 17°C | 7°C | 12.3°C | 84 mm |
| September | 13°C | 3°C | 8.0°C | 88 mm |
| October | 5°C | −4°C | 0.8°C | 57 mm |
| November | −1°C | −9°C | −5.3°C | 77 mm |
| December | −4°C | −13°C | −8.5°C | 55 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. Port Alsworth's own co-op station Port Alsworth station does: 88 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USW00026562; 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 Port Alsworth?
Normal highs sit between 65°F and 85°F in June and July.
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 USW00026562.
When is the last frost in Port Alsworth?
In Port Alsworth, the last spring frost (32°F) comes after June 2 in half of years and after June 13 in one year in ten; the first autumn frost comes before September 12 in half of years and before August 29 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
- June 21 year in 10 after June 13; 9 in 10 after May 22
- First autumn frost, half of years before
- September 121 year in 10 before August 29; 9 in 10 before September 25
NOAA puts the median frost-free season at 101 days, and the season without a hard freeze (28°F) at 129 days.
A hard freeze (28°F) comes after May 19 in half of springs and before September 25 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Port Alsworth in zone 4a in ZIP code 99653.
Frost dates for every NOAA station in Alaska · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00026562; 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 in Port Alsworth?
In a normal year in Port Alsworth, a 90°F day is rare and 209 nights fall to 32°F or colder.
- Days at 90°F or more
- fewer than 1a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 209a normal year
- Days that stay below freezing
- 79high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USW00026562.
How sunny is Port Alsworth?
Over a year 64% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Port Alsworth, 2.6 kWh per square metre a day. March is the sunniest month (78%) and October the cloudiest (56%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 66% | 0.4 |
| February | 64% | 1.1 |
| March | 78% | 2.8 |
| April | 74% | 4.3 |
| May | 66% | 4.9 |
| June | 64% | 5.2 |
| July | 59% | 4.4 |
| August | 59% | 3.5 |
| September | 58% | 2.3 |
| October | 56% | 1.1 |
| November | 57% | 0.4 |
| December | 61% | 0.2 |
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 Port Alsworth need?
A normal year in Port Alsworth brings 10,991 heating degree days, 2.0 times the median U.S. place (5,373), and 4 cooling degree days, 100% fewer than the median (908). Eleven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 497 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,572 | 0 |
| February | 1,271 | 0 |
| March | 1,358 | 0 |
| April | 899 | 0 |
| May | 622 | 0 |
| June | 358 | 1 |
| July | 264 | 3 |
| August | 336 | 0 |
| September | 557 | 0 |
| October | 980 | 0 |
| November | 1,279 | 0 |
| December | 1,497 | 0 |
| Year (annual) | 10,991 | 4 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00026562. 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 Port Alsworth been warmer than normal lately?
2025 averaged 37.3°F, 2.5°F above the 1991-2020 normal of 34.8°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 33.2°F | −1.6°F | 25.54 |
| 2022 | 36.4°F | +1.6°F | 29.50 |
| 2023 | 34.3°F | −0.5°F | 23.01 |
| 2024 | 35.4°F | +0.6°F | 19.16 |
| 2025 | 37.3°F | +2.5°F | 18.39 |
Source: observed years: ACIS, station USW00026562. A year counts only with all twelve months complete.
How does Port Alsworth's climate compare?
Port Alsworth is warmer than 41 of the other 84 places with their own NOAA record in Alaska, and wetter than 42. Across the 7,247 U.S. stations with normals, its annual mean of 34.8°F is warmer than 2%.
In the Köppen classification computed from these normals, Port Alsworth is Dsc: continental, dry-summer, cool 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.
What do Port Alsworth's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Port Alsworth. This page uses Port Alsworth (1 mi SW); the other differs by site and elevation:
| Station | From the center | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Port Alsworth station USC00507570 | 3 mi N | 260 ft | 38.4°F | 10°F | 69°F | 13.1 | 88 | May 12 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Port Alsworth's climate
What is the coldest month in Port Alsworth?
January, with a normal high of 24°F and a normal low of 5°F. The warmest is July (67°F by day, 46°F at night).
Does it snow in Port Alsworth?
Yes. NOAA publishes no 1991-2020 snowfall normal for Port Alsworth's NOAA station; Port Alsworth's own co-op station Port Alsworth station records 88 inches of snow in a normal year.
What is the rainiest month in Port Alsworth?
September, with 3.48 in of precipitation in a normal year; the driest is May with 0.84 in.
What plant hardiness zone is Port Alsworth in?
The USDA's 2023 map puts Port Alsworth in zone 4a in ZIP code 99653.
How late can frost come in Port Alsworth?
In half of years the last 32°F night comes after June 2; in one year in ten it comes after June 13. Waiting until June 13 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Alaska climateThe statewide normals and every place in the state
- Iliamna, AK37 miles from this station, 37.7°F a year
- Intricate Bay, AK45 miles from this station, 36.7°F a year
- Big River Lakes, AK81 miles from this station, 39.5°F a year
- Seldovia, AK105 miles from this station, 39.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made