Main Bay, Alaska climate: Climate normals at a NOAA weather station
Main Bay's normal year runs from 21°F January nights to 62°F July afternoons, with 206.9 inches of precipitation and 262 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 4.2°C, January lows of −6°C, July highs of 17°C, 5,255 mm of precipitation a year.
- NOAA stationMain Bay
- Station IDUSC00505604
- Location60.52°N 148.09°W
- Elevation57 ft (17 m)
On October 23, the normal high in Main Bay is 43°F and the normal low 32°F, and the chance of measurable rain or snow is 70%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Main Bay.
- Jan 31° 21°
- Feb 33° 22°
- Mar 37° 22°
- Apr 44° 30°
- May 52° 35°
- Jun 59° 43°
- Jul 62° 50°
- Aug 61° 49°
- Sep 55° 43°
- Oct 45° 34°
- Nov 36° 26°
- Dec 33° 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 at Main Bay each month?
July is the warmest month, with normal highs of 62°F; January the coldest, with normal lows of 21°F. The most precipitation falls in September (24.85 in), the least in June (7.89 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 31°F | 21°F | 26.0°F | 18.78 | 55.3 | 19 | <1 | 28 | 6 h 30 min |
| February | 33°F | 22°F | 27.3°F | 16.74 | 48.6 | 18 | <1 | 25 | 9 h |
| March | 37°F | 22°F | 29.6°F | 14.25 | 57.4 | 17 | <1 | 28 | 11 h 40 min |
| April | 44°F | 30°F | 36.8°F | 14.12 | 11.8 | 17 | <1 | 19 | 14 h 30 min |
| May | 52°F | 35°F | 43.2°F | 13.20 | 0.5 | 17 | <1 | 7 | 17 h 10 min |
| June | 59°F | 43°F | 51.1°F | 7.89 | 0.0 | 16 | <1 | <1 | 19 h |
| July | 62°F | 50°F | 56.0°F | 10.92 | 0.0 | 18 | <1 | <1 | 18 h 20 min |
| August | 61°F | 49°F | 55.3°F | 17.26 | 0.0 | 19 | <1 | <1 | 15 h 50 min |
| September | 55°F | 43°F | 49.1°F | 24.85 | 0.0 | 23 | <1 | 1 | 13 h |
| October | 45°F | 34°F | 39.7°F | 24.80 | 4.3 | 22 | <1 | 13 | 10 h 20 min |
| November | 36°F | 26°F | 31.2°F | 21.04 | 25.7 | 19 | <1 | 23 | 7 h 30 min |
| December | 33°F | 24°F | 28.4°F | 23.04 | 58.2 | 22 | <1 | 27 | 5 h 50 min |
| Year (annual) | 46°F | 33°F | 39.5°F | 206.89 | 261.8 | 227 | <1 | 172 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 0°C | −6°C | −3.3°C | 477 mm | 140 cm |
| February | 0°C | −6°C | −2.6°C | 425 mm | 123 cm |
| March | 3°C | −5°C | −1.3°C | 362 mm | 146 cm |
| April | 7°C | −1°C | 2.7°C | 359 mm | 30 cm |
| May | 11°C | 2°C | 6.2°C | 335 mm | 1 cm |
| June | 15°C | 6°C | 10.6°C | 200 mm | 0 cm |
| July | 17°C | 10°C | 13.3°C | 277 mm | 0 cm |
| August | 16°C | 10°C | 12.9°C | 438 mm | 0 cm |
| September | 13°C | 6°C | 9.5°C | 631 mm | 0 cm |
| October | 7°C | 1°C | 4.3°C | 630 mm | 11 cm |
| November | 2°C | −3°C | −0.4°C | 534 mm | 65 cm |
| December | 1°C | −5°C | −2.0°C | 585 mm | 148 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00505604; 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 Main Bay?
No month's normal high reaches 65°F in Main Bay: the warmest is July at 62°F.
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 USC00505604.
When is the last frost at Main Bay?
In Main Bay, the last spring frost (32°F) comes after May 19 in half of years and after June 4 in one year in ten; the first autumn frost comes before October 6 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 191 year in 10 after June 4; 9 in 10 after May 2
- First autumn frost, half of years before
- October 61 year in 10 before September 24; 9 in 10 before October 22
NOAA puts the median frost-free season at 139 days, and the season without a hard freeze (28°F) at 176 days.
A hard freeze (28°F) comes after April 28 in half of springs and before October 20 in half of autumns.
By the USDA's method, the average of each year's coldest night over 1991-2020, the station is in plant hardiness zone 6b: the coldest night of a typical year reaches 0°F (26 complete years).
Frost dates for every NOAA station in Alaska · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00505604; 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 at Main Bay?
In a normal year in Main Bay, a 90°F day is rare, 172 nights fall to 32°F or colder and 227 days bring measurable precipitation.
- 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
- 172a normal year
- Days that stay below freezing
- 51high of 32°F or less
- Days with 0.01 inch of precipitation
- 227a normal year
- Days with 1 inch of snow or more
- 50a normal year
The highest temperature in this station's record (since 1982) is 86°F, on June 27, 1997; the lowest is −13°F, on February 4, 1999.
The wettest calendar year on that record is 2025, with 260.26 in; the snowiest season is 2011–12, with 515.2 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00505604; records: ACIS (NOAA Regional Climate Centers), station USC00505604. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Main Bay?
Over a year 59% of the sunlight that would reach the ground under clear skies gets through the clouds at Main Bay, 2.4 kWh per square metre a day. March is the sunniest month (64%) and November the cloudiest (52%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 53% | 0.3 |
| February | 55% | 0.9 |
| March | 64% | 2.3 |
| April | 61% | 3.6 |
| May | 61% | 4.6 |
| June | 59% | 4.9 |
| July | 60% | 4.6 |
| August | 58% | 3.5 |
| September | 57% | 2.3 |
| October | 53% | 1.1 |
| November | 52% | 0.4 |
| December | 53% | 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 many heating and cooling degree days does Main Bay record?
A normal year at Main Bay brings 9,293 heating degree days, 73% more than the median U.S. place (5,373), and 2 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 468 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,207 | 0 |
| February | 1,057 | 0 |
| March | 1,097 | 0 |
| April | 845 | 0 |
| May | 674 | 0 |
| June | 419 | 0 |
| July | 280 | 1 |
| August | 301 | 0 |
| September | 477 | 0 |
| October | 786 | 0 |
| November | 1,014 | 0 |
| December | 1,136 | 0 |
| Year (annual) | 9,293 | 2 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00505604. 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.
Have recent years at Main Bay been warmer than normal?
2025 averaged 40.7°F, 1.2°F above the 1991-2020 normal of 39.5°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 37.8°F | −1.7°F | 184.97 | 288.5 |
| 2022 | 39.6°F | +0.1°F | 208.88 | 298.1 |
| 2025 | 40.7°F | +1.2°F | 260.26 | 116.2 |
Source: observed years: ACIS, station USC00505604. A year counts only with all twelve months complete.
How does Main Bay's climate compare?
Main Bay is warmer than 57 of the 85 places with their own NOAA record in Alaska, and wetter than 74. Across the 7,247 U.S. stations with normals, its annual mean of 39.5°F is warmer than 5%.
In the Köppen classification computed from these normals, Main Bay is Dfc: continental, no dry season, 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.
Questions about Main Bay's climate
What is the coldest month at Main Bay?
January, with a normal high of 31°F and a normal low of 21°F. The warmest is July (62°F by day, 50°F at night).
Does it snow at Main Bay?
Yes: 262 inches in a normal year, falling on 63 days with 0.1 inch or more, the most in December (58.2 inches).
What is the rainiest month at Main Bay?
September, with 24.85 in of precipitation in a normal year; the driest is June with 7.89 in.
What plant hardiness zone is Main Bay in?
By the same method at the station, the coldest night of a typical year reaches 0°F (26 years, 1991-2020): zone 6b.
How late can frost come at Main Bay?
In half of years the last 32°F night comes after May 19; in one year in ten it comes after June 4. Waiting until June 4 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Alaska climateThe statewide normals and every place in the state
- Wally Noerenberg Hatchery, AK19 miles from this station, 40.0°F a year
- Whittier, AK27 miles from this station, 41.1°F a year
- Portage Glacier V C, AK31 miles from this station, 37.1°F a year
- Port San Juan, AK32 miles from this station, 40.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made