Chinook, Montana climate: Normal weather by month, frost dates and records
Chinook's normal year runs from 4°F January nights to 84°F July afternoons, with 13.4 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 5.8°C, January lows of −15°C, July highs of 29°C, 341 mm of precipitation a year.
- NOAA stationChinook
- Station IDUSC00241722
- Location48.59°N 109.23°W
- Elevation2,420 ft (738 m)
- Population1,162
On October 22, the normal high in Chinook is 53°F and the normal low 26°F, and the chance of measurable rain or snow is 18%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Chinook.
- Jan 27° 4°
- Feb 31° 7°
- Mar 43° 18°
- Apr 57° 29°
- May 67° 40°
- Jun 75° 49°
- Jul 84° 54°
- Aug 83° 52°
- Sep 72° 41°
- Oct 57° 29°
- Nov 41° 17°
- Dec 31° 8°
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 Chinook each month?
July is the warmest month, with normal highs of 84°F; January the coldest, with normal lows of 4°F. The most precipitation falls in June (2.86 in), the least in February (0.37 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 27°F | 4°F | 15.7°F | 0.45 | 5 | <1 | 30 | 8 h 40 min |
| February | 31°F | 7°F | 19.2°F | 0.37 | 5 | <1 | 28 | 10 h 10 min |
| March | 43°F | 18°F | 30.4°F | 0.59 | 5 | <1 | 29 | 11 h 50 min |
| April | 57°F | 29°F | 43.1°F | 1.04 | 6 | <1 | 20 | 13 h 40 min |
| May | 67°F | 40°F | 53.5°F | 2.42 | 10 | 1 | 6 | 15 h 10 min |
| June | 75°F | 49°F | 62.4°F | 2.86 | 11 | 2 | <1 | 16 h 10 min |
| July | 84°F | 54°F | 69.0°F | 1.62 | 7 | 10 | <1 | 15 h 50 min |
| August | 83°F | 52°F | 67.5°F | 1.14 | 5 | 10 | <1 | 14 h 30 min |
| September | 72°F | 41°F | 56.8°F | 0.99 | 7 | 2 | 3 | 12 h 40 min |
| October | 57°F | 29°F | 42.7°F | 0.88 | 6 | <1 | 20 | 10 h 50 min |
| November | 41°F | 17°F | 29.2°F | 0.69 | 6 | <1 | 28 | 9 h 20 min |
| December | 31°F | 8°F | 19.0°F | 0.39 | 5 | <1 | 31 | 8 h 20 min |
| Year (annual) | 56°F | 29°F | 42.4°F | 13.44 | 77 | 24 | 195 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −3°C | −15°C | −9.1°C | 11 mm |
| February | 0°C | −14°C | −7.1°C | 9 mm |
| March | 6°C | −8°C | −0.9°C | 15 mm |
| April | 14°C | −1°C | 6.2°C | 26 mm |
| May | 19°C | 4°C | 11.9°C | 61 mm |
| June | 24°C | 10°C | 16.9°C | 73 mm |
| July | 29°C | 12°C | 20.6°C | 41 mm |
| August | 29°C | 11°C | 19.7°C | 29 mm |
| September | 22°C | 5°C | 13.8°C | 25 mm |
| October | 14°C | −2°C | 5.9°C | 22 mm |
| November | 5°C | −8°C | −1.6°C | 18 mm |
| December | −1°C | −14°C | −7.2°C | 10 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Havre (25 miles away), gets 41 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00241722; 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 Chinook?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, August has the fewest days with rain (5).
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 USC00241722.
When is the last frost in Chinook?
In Chinook, the last spring frost (32°F) comes after May 14 in half of years and after May 27 in one year in ten; the first autumn frost comes before September 23 in half of years and before September 11 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 141 year in 10 after May 27; 9 in 10 after May 1
- First autumn frost, half of years before
- September 231 year in 10 before September 11; 9 in 10 before October 3
NOAA puts the median frost-free season at 130 days, and the season without a hard freeze (28°F) at 149 days.
A hard freeze (28°F) comes after May 3 in half of springs and before October 1 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Chinook in zone 3b in ZIP code 59523, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Chinook's NOAA station is in zone 3b: the coldest night of a typical year reaches −32°F (26 complete years).
Frost dates for every NOAA station in Montana · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00241722; 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 Chinook?
In a normal year in Chinook, 24 days a year reach 90°F (1 of them 100°F or more), 195 nights fall to 32°F or colder and 77 days bring measurable precipitation.
- Days at 90°F or more
- 24a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 195a normal year
- Days that stay below freezing
- 59high of 32°F or less
- Days with 0.01 inch of precipitation
- 77a normal year
The highest temperature in this station's record (since 1895) is 110°F, on July 27, 1917; the lowest is −53°F, on December 21, 1989.
The wettest calendar year on that record is 1927, with 21.55 in; the snowiest season is 2010–11, with 66.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00241722; records: ACIS (NOAA Regional Climate Centers), station USC00241722. Records use complete months only; a month missing more than three days is left out.
How sunny is Chinook?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Chinook, 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 much heating and cooling does Chinook need?
A normal year in Chinook brings 8,571 heating degree days, 60% more than the median U.S. place (5,373), and 351 cooling degree days, 61% 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 1,979 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,530 | 0 |
| February | 1,284 | 0 |
| March | 1,074 | 0 |
| April | 656 | 0 |
| May | 364 | 8 |
| June | 123 | 43 |
| July | 28 | 151 |
| August | 54 | 132 |
| September | 265 | 17 |
| October | 692 | 0 |
| November | 1,076 | 0 |
| December | 1,426 | 0 |
| Year (annual) | 8,571 | 351 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00241722. 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 Chinook been warmer than normal lately?
Over 66 complete years from 1917 to 2024, the station's annual mean temperature rose at a fitted 1.8°F per century (+0.10°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Chinook's climate compare?
Chinook is warmer than 37 of the other 140 places with their own NOAA record in Montana, and wetter than 41. Across the 7,247 U.S. stations with normals, its annual mean of 42.4°F is warmer than 10%.
In the Köppen classification computed from these normals, Chinook 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 Chinook share this climate record?
2 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.
- Zurich, MT45 people · 9 mi E
- Hartland Colony, MT0 people · 27 mi N
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 Chinook's climate
What is the coldest month in Chinook?
January, with a normal high of 27°F and a normal low of 4°F. The warmest is July (84°F by day, 54°F at night).
Does it snow in Chinook?
Yes. NOAA publishes no 1991-2020 snowfall normal for Chinook's NOAA station; the nearest record that keeps one, Havre (25 miles away), records 41 inches of snow in a normal year.
What is the rainiest month in Chinook?
June, with 2.86 in of precipitation in a normal year; the driest is February with 0.37 in.
What plant hardiness zone is Chinook in?
The USDA's 2023 map puts Chinook in zone 3b in ZIP code 59523, the nearest ZIP area. By the same method at Chinook's NOAA station, the coldest night of a typical year reaches −32°F (26 years, 1991-2020): zone 3b.
How late can frost come in Chinook?
In half of years the last 32°F night comes after May 14; in one year in ten it comes after May 27. Waiting until May 27 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Harlem, MT20 miles from this station, 43.5°F a year
- Fort Belknap (2 mi SW), MT22 miles from this station, 42.6°F a year
- Havre, MT25 miles from this station, 43.6°F a year
- Fort Assiniboine, MT27 miles from this station, 43.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made