Fort Assiniboine, Montana climate: Climate normals at a NOAA weather station
Fort Assiniboine's normal year runs from 7°F January nights to 85°F July afternoons, with 13.1 inches of precipitation and 35 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.4°C, January lows of −14°C, July highs of 30°C, 334 mm of precipitation a year.
- NOAA stationFort Assiniboine
- Station IDUSC00243110
- Location48.50°N 109.80°W
- Elevation2,675 ft (815 m)
On October 22, the normal high in Fort Assiniboine is 54°F and the normal low 28°F, and the chance of measurable rain or snow is 21%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Fort Assiniboine.
- Jan 28° 7°
- Feb 33° 10°
- Mar 44° 19°
- Apr 57° 31°
- May 67° 40°
- Jun 75° 49°
- Jul 85° 54°
- Aug 84° 52°
- Sep 73° 43°
- Oct 58° 31°
- Nov 42° 20°
- Dec 32° 11°
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 Fort Assiniboine each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 7°F. The most precipitation falls in June (2.93 in), the least in February (0.34 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 28°F | 7°F | 17.8°F | 0.42 | 6.4 | 7 | <1 | 29 | 8 h 40 min |
| February | 33°F | 10°F | 21.5°F | 0.34 | 7.3 | 5 | <1 | 27 | 10 h 10 min |
| March | 44°F | 19°F | 31.7°F | 0.47 | 4.0 | 5 | <1 | 27 | 11 h 50 min |
| April | 57°F | 31°F | 43.7°F | 1.18 | 2.7 | 8 | <1 | 17 | 13 h 40 min |
| May | 67°F | 40°F | 53.6°F | 2.12 | 0.7 | 11 | 1 | 5 | 15 h 10 min |
| June | 75°F | 49°F | 61.7°F | 2.93 | 0.0 | 13 | 2 | <1 | 16 h 10 min |
| July | 85°F | 54°F | 69.5°F | 1.67 | 0.0 | 8 | 11 | <1 | 15 h 50 min |
| August | 84°F | 52°F | 68.2°F | 0.96 | 0.0 | 7 | 11 | <1 | 14 h 20 min |
| September | 73°F | 43°F | 57.9°F | 1.18 | 0.0 | 7 | 3 | 2 | 12 h 40 min |
| October | 58°F | 31°F | 44.2°F | 0.89 | 1.9 | 7 | <1 | 17 | 11 h |
| November | 42°F | 20°F | 31.0°F | 0.62 | 5.2 | 6 | <1 | 26 | 9 h 20 min |
| December | 32°F | 11°F | 21.1°F | 0.36 | 6.4 | 5 | <1 | 30 | 8 h 20 min |
| Year (annual) | 57°F | 31°F | 43.5°F | 13.14 | 34.6 | 88 | 27 | 179 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −2°C | −14°C | −7.9°C | 11 mm | 16 cm |
| February | 0°C | −12°C | −5.8°C | 9 mm | 19 cm |
| March | 7°C | −7°C | −0.2°C | 12 mm | 10 cm |
| April | 14°C | −1°C | 6.5°C | 30 mm | 7 cm |
| May | 19°C | 5°C | 12.0°C | 54 mm | 2 cm |
| June | 24°C | 9°C | 16.5°C | 74 mm | 0 cm |
| July | 30°C | 12°C | 20.8°C | 42 mm | 0 cm |
| August | 29°C | 11°C | 20.1°C | 24 mm | 0 cm |
| September | 23°C | 6°C | 14.4°C | 30 mm | 0 cm |
| October | 14°C | −1°C | 6.8°C | 23 mm | 5 cm |
| November | 6°C | −7°C | −0.6°C | 16 mm | 13 cm |
| December | 0°C | −12°C | −6.1°C | 9 mm | 16 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243110; 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 Fort Assiniboine?
Normal highs sit between 65°F and 85°F in May, June, August and September. Of those, August 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 USC00243110.
When is the last frost at Fort Assiniboine?
In Fort Assiniboine, the last spring frost (32°F) comes after May 15 in half of years and after May 28 in one year in ten; the first autumn frost comes before September 24 in half of years and before September 8 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 151 year in 10 after May 28; 9 in 10 after May 4
- First autumn frost, half of years before
- September 241 year in 10 before September 8; 9 in 10 before October 4
NOAA puts the median frost-free season at 130 days, and the season without a hard freeze (28°F) at 150 days.
A hard freeze (28°F) comes after May 4 in half of springs and before October 2 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Fort Assiniboine in zone 3b in ZIP code 59501, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 4a: the coldest night of a typical year reaches −28°F (27 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 Montana · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00243110; 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 at Fort Assiniboine?
In a normal year in Fort Assiniboine, 27 days a year reach 90°F (2 of them 100°F or more), 179 nights fall to 32°F or colder and 88 days bring measurable precipitation.
- Days at 90°F or more
- 27a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 179a normal year
- Days that stay below freezing
- 55high of 32°F or less
- Days with 0.01 inch of precipitation
- 88a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in this station's record (since 1917) is 111°F, on August 6, 1961; the lowest is −49°F, on January 24, 1969.
The wettest calendar year on that record is 1975, with 21.34 in; the snowiest season is 2017–18, with 92.9 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00243110; records: ACIS (NOAA Regional Climate Centers), station USC00243110. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Fort Assiniboine?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds at Fort Assiniboine, 4.0 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (69%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 75% | 1.5 |
| February | 78% | 2.6 |
| March | 75% | 3.8 |
| April | 73% | 4.9 |
| May | 74% | 5.9 |
| June | 78% | 6.6 |
| July | 87% | 7.0 |
| August | 85% | 5.8 |
| September | 79% | 4.2 |
| October | 74% | 2.7 |
| November | 71% | 1.6 |
| December | 69% | 1.1 |
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 Fort Assiniboine record?
A normal year at Fort Assiniboine brings 8,198 heating degree days, 53% more than the median U.S. place (5,373), and 397 cooling degree days, 56% 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 2,070 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,465 | 0 |
| February | 1,219 | 0 |
| March | 1,032 | 0 |
| April | 638 | 0 |
| May | 361 | 8 |
| June | 138 | 41 |
| July | 30 | 169 |
| August | 51 | 151 |
| September | 239 | 26 |
| October | 646 | 1 |
| November | 1,019 | 0 |
| December | 1,361 | 0 |
| Year (annual) | 8,198 | 397 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243110. 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 Fort Assiniboine been warmer than normal?
2025 averaged 44.0°F, 0.5°F above the 1991-2020 normal of 43.5°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 44.5°F | +1.0°F | 7.52 | – |
| 2022 | 42.6°F | −0.9°F | 10.47 | 32.3 |
| 2023 | 44.5°F | +1.0°F | 11.20 | 25.0 |
| 2024 | 43.9°F | +0.4°F | 14.58 | 17.9 |
| 2025 | 44.0°F | +0.5°F | 14.14 | 15.5 |
Over 101 complete years from 1880 to 2025, the station's annual mean temperature rose at a fitted 1.9°F per century (+0.10°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00243110; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Fort Assiniboine's climate compare?
Fort Assiniboine is warmer than 56 of the 141 places with their own NOAA record in Montana, and wetter than 33. Across the 7,247 U.S. stations with normals, its annual mean of 43.5°F is warmer than 14%.
In the Köppen classification computed from these normals, Fort Assiniboine is BSk: cold semi-arid steppe. 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 Fort Assiniboine 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.
- Azure, MT454 people · 13 mi S
- Sangrey, MT400 people · 15 mi S
- Laredo, MT0 people · 6 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 Fort Assiniboine's climate
What is the coldest month at Fort Assiniboine?
January, with a normal high of 28°F and a normal low of 7°F. The warmest is July (85°F by day, 54°F at night).
Does it snow at Fort Assiniboine?
Yes: 35 inches in a normal year, falling on 26 days with 0.1 inch or more, the most in February (7.3 inches).
What is the rainiest month at Fort Assiniboine?
June, with 2.93 in of precipitation in a normal year; the driest is February with 0.34 in.
What plant hardiness zone is Fort Assiniboine in?
The USDA's 2023 map puts Fort Assiniboine in zone 3b in ZIP code 59501, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −28°F (27 years, 1991-2020): zone 4a.
How late can frost come at Fort Assiniboine?
In half of years the last 32°F night comes after May 15; in one year in ten it comes after May 28. Waiting until May 28 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Havre, MT4 miles from this station, 43.6°F a year
- Gildford, MT24 miles from this station, 41.7°F a year
- Chinook, MT27 miles from this station, 42.4°F a year
- Big Sandy, MT28 miles from this station, 45.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made