Iliamna, Alaska climate: Normal weather by month, frost dates and records
Iliamna's normal year runs from 12°F January nights to 65°F July afternoons, with 25.0 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 3.2°C, January lows of −11°C, July highs of 18°C, 635 mm of precipitation a year.
- NOAA stationIliamna Airport
- Station IDUSW00025506
- Location59.75°N 154.91°W
- Elevation143 ft (44 m)
- Population (census place)45
On October 22, the normal high in Iliamna is 42°F and the normal low 30°F, and the chance of measurable rain or snow is 41%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Iliamna.
- Jan 25° 12°
- Feb 30° 16°
- Mar 32° 16°
- Apr 43° 29°
- May 55° 38°
- Jun 62° 45°
- Jul 65° 51°
- Aug 64° 50°
- Sep 56° 43°
- Oct 45° 32°
- Nov 33° 21°
- Dec 28° 15°
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 Iliamna each month?
July is the warmest month, with normal highs of 65°F; January the coldest, with normal lows of 12°F. The most precipitation falls in September (5.01 in), the least in April (0.83 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 25°F | 12°F | 18.4°F | 0.90 | 8 | <1 | 26 | 6 h 40 min |
| February | 30°F | 16°F | 23.1°F | 1.06 | 9 | <1 | 23 | 9 h 10 min |
| March | 32°F | 16°F | 23.7°F | 0.84 | 8 | <1 | 27 | 11 h 40 min |
| April | 43°F | 29°F | 36.1°F | 0.83 | 8 | <1 | 20 | 14 h 30 min |
| May | 55°F | 38°F | 46.3°F | 1.19 | 9 | <1 | 6 | 17 h |
| June | 62°F | 45°F | 53.7°F | 1.51 | 10 | <1 | <1 | 18 h 40 min |
| July | 65°F | 51°F | 57.8°F | 3.08 | 13 | <1 | <1 | 18 h |
| August | 64°F | 50°F | 56.7°F | 4.14 | 16 | <1 | <1 | 15 h 40 min |
| September | 56°F | 43°F | 49.7°F | 5.01 | 16 | <1 | 2 | 13 h |
| October | 45°F | 32°F | 38.4°F | 2.84 | 13 | <1 | 16 | 10 h 20 min |
| November | 33°F | 21°F | 27.1°F | 2.16 | 12 | <1 | 24 | 7 h 40 min |
| December | 28°F | 15°F | 21.7°F | 1.45 | 11 | <1 | 26 | 6 h |
| Year (annual) | 45°F | 31°F | 37.7°F | 25.01 | 132 | <1 | 170 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −4°C | −11°C | −7.6°C | 23 mm |
| February | −1°C | −9°C | −4.9°C | 27 mm |
| March | 0°C | −9°C | −4.6°C | 21 mm |
| April | 6°C | −2°C | 2.3°C | 21 mm |
| May | 13°C | 3°C | 7.9°C | 30 mm |
| June | 17°C | 7°C | 12.1°C | 38 mm |
| July | 18°C | 10°C | 14.3°C | 78 mm |
| August | 18°C | 10°C | 13.7°C | 105 mm |
| September | 13°C | 6°C | 9.8°C | 127 mm |
| October | 7°C | 0°C | 3.6°C | 72 mm |
| November | 1°C | −6°C | −2.7°C | 55 mm |
| December | −2°C | −9°C | −5.7°C | 37 mm |
NOAA publishes no 1991-2020 snowfall normal for this station, and no record within 25 miles keeps one, so snow is left out here rather than estimated.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00025506; 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 Iliamna?
No month's normal high reaches 65°F in Iliamna: the warmest is July at 65°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 USW00025506.
When is the last frost in Iliamna?
In Iliamna, the last spring frost (32°F) comes after May 10 in half of years and after May 25 in one year in ten; the first autumn frost comes before October 1 in half of years and before September 17 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 101 year in 10 after May 25; 9 in 10 after April 28
- First autumn frost, half of years before
- October 11 year in 10 before September 17; 9 in 10 before October 15
NOAA puts the median frost-free season at 144 days, and the season without a hard freeze (28°F) at 166 days.
A hard freeze (28°F) comes after April 28 in half of springs and before October 10 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Iliamna in zone 4b in ZIP code 99606. By the map's own method, the average of each year's coldest night over 1991-2020, Iliamna's NOAA station is in zone 5a: the coldest night of a typical year reaches −20°F (26 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Alaska · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00025506; 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 Iliamna?
In a normal year in Iliamna, a 90°F day is rare, 170 nights fall to 32°F or colder and 132 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
- 170a normal year
- Days that stay below freezing
- 82high of 32°F or less
- Days with 0.01 inch of precipitation
- 132a normal year
The highest temperature in this station's record (since 1920) is 91°F, on June 27, 1953; the lowest is −47°F, on January 22, 1947.
The wettest calendar year on that record is 1985, with 40.79 in; the snowiest season is 1948–49, with 123.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00025506; records: ACIS (NOAA Regional Climate Centers), station USW00025506. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Iliamna, and how clear are its skies?
The summer (June-August) dew point averages 47°F. The muggiest month is July, with an average dew point of 50°F; the driest air comes in January (11°F). November is the windiest month (11.7 mph on average), and February has the most clear or nearly clear hours (40%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 11°F | 77% | 72% | 10.7 mph | 37% | 42% |
| February | 16°F | 73% | 65% | 9.9 mph | 40% | 40% |
| March | 20°F | 72% | 62% | 9.0 mph | 37% | 40% |
| April | 30°F | 68% | 56% | 8.8 mph | 33% | 40% |
| May | 39°F | 67% | 54% | 8.8 mph | 39% | 35% |
| June | 47°F | 76% | 62% | 7.9 mph | 35% | 43% |
| July | 50°F | 79% | 69% | 8.2 mph | 23% | 58% |
| August | 46°F | 78% | 67% | 8.5 mph | 25% | 49% |
| September | 36°F | 75% | 64% | 10.1 mph | 34% | 45% |
| October | 24°F | 76% | 69% | 10.8 mph | 35% | 42% |
| November | 17°F | 77% | 76% | 11.7 mph | 30% | 50% |
| December | 13°F | 78% | 77% | 11.4 mph | 35% | 45% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00025506. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is Iliamna?
Over a year 61% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Iliamna, 2.5 kWh per square metre a day. June is the sunniest month (66%) and December the cloudiest (49%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 52% | 0.3 |
| February | 52% | 0.9 |
| March | 63% | 2.3 |
| April | 62% | 3.6 |
| May | 64% | 4.7 |
| June | 66% | 5.3 |
| July | 60% | 4.5 |
| August | 60% | 3.6 |
| September | 59% | 2.4 |
| October | 58% | 1.3 |
| November | 54% | 0.5 |
| December | 49% | 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 Iliamna need?
A normal year in Iliamna brings 9,940 heating degree days, 85% more than the median U.S. place (5,373), and 8 cooling degree days, 99% fewer than the median (908). Ten months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 655 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,446 | 0 |
| February | 1,173 | 0 |
| March | 1,280 | 0 |
| April | 869 | 0 |
| May | 580 | 0 |
| June | 341 | 2 |
| July | 228 | 5 |
| August | 259 | 2 |
| September | 461 | 0 |
| October | 823 | 0 |
| November | 1,137 | 0 |
| December | 1,344 | 0 |
| Year (annual) | 9,940 | 8 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00025506. 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 Iliamna been warmer than normal lately?
2024 averaged 34.8°F, 2.9°F below the 1991-2020 normal of 37.7°F. 0 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 33.8°F | −3.9°F | 24.06 |
| 2022 | 37.3°F | −0.4°F | 33.76 |
| 2024 | 34.8°F | −2.9°F | 25.24 |
Over 68 complete years from 1943 to 2024, the station's annual mean temperature rose at a fitted 5.3°F per century (+0.30°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00025506; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Iliamna's climate compare?
Iliamna is warmer than 55 of the other 84 places with their own NOAA record in Alaska, and wetter than 45. Across the 7,247 U.S. stations with normals, its annual mean of 37.7°F is warmer than 3%.
In the Köppen classification computed from these normals, Iliamna 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.
Which places near Iliamna share this climate record?
3 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.
- Newhalen, AK149 people · 1 mi S
- Nondalton, AK116 people · 16 mi N
- Igiugig, AK68 people · 46 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 Iliamna's climate
What is the coldest month in Iliamna?
January, with a normal high of 25°F and a normal low of 12°F. The warmest is July (65°F by day, 51°F at night).
What is the rainiest month in Iliamna?
September, with 5.01 in of precipitation in a normal year; the driest is April with 0.83 in.
What plant hardiness zone is Iliamna in?
The USDA's 2023 map puts Iliamna in zone 4b in ZIP code 99606. By the same method at Iliamna's NOAA station, the coldest night of a typical year reaches −20°F (26 years, 1991-2020): zone 5a.
How late can frost come in Iliamna?
In half of years the last 32°F night comes after May 10; in one year in ten it comes after May 25. Waiting until May 25 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Iliamna in OctoberThis month day by day, its records and recent years
- Alaska climateThe statewide normals and every place in the state
- Intricate Bay, AK20 miles from this station, 36.7°F a year
- Port Alsworth, AK37 miles from this station, 34.8°F a year
- King Salmon, AK96 miles from this station, 36.5°F a year
- King Salmon (42 mi SE), AK112 miles from this station, 35.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made