Colstrip, Montana climate: Normal weather by month, frost dates and records
Colstrip's normal year runs from 14°F January nights to 85°F July afternoons, with 16.4 inches of precipitation and 37 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.8°C, January lows of −10°C, July highs of 29°C, 417 mm of precipitation a year.
- NOAA stationColstrip
- Station IDUSC00241905
- Location45.89°N 106.63°W
- Elevation3,218 ft (981 m)
- Population2,063
On October 24, the normal high in Colstrip is 54°F and the normal low 31°F, and the chance of measurable rain or snow is 22%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Colstrip.
- Jan 36° 14°
- Feb 37° 15°
- Mar 47° 24°
- Apr 55° 32°
- May 65° 42°
- Jun 75° 51°
- Jul 85° 57°
- Aug 84° 55°
- Sep 73° 46°
- Oct 58° 34°
- Nov 46° 24°
- Dec 37° 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 Colstrip each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 14°F. The most precipitation falls in May (3.14 in), the least in December (0.56 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 36°F | 14°F | 24.7°F | 0.65 | 7.4 | 7 | <1 | 29 | 9 h |
| February | 37°F | 15°F | 26.1°F | 0.69 | 7.3 | 6 | <1 | 26 | 10 h 20 min |
| March | 47°F | 24°F | 35.5°F | 0.95 | 5.5 | 8 | <1 | 24 | 11 h 50 min |
| April | 55°F | 32°F | 43.7°F | 1.92 | 3.3 | 9 | <1 | 14 | 13 h 30 min |
| May | 65°F | 42°F | 53.4°F | 3.14 | 0.5 | 12 | <1 | 4 | 14 h 50 min |
| June | 75°F | 51°F | 62.9°F | 2.48 | 0.0 | 11 | 2 | <1 | 15 h 40 min |
| July | 85°F | 57°F | 71.1°F | 1.42 | 0.0 | 7 | 10 | <1 | 15 h 20 min |
| August | 84°F | 55°F | 69.6°F | 1.03 | 0.0 | 6 | 9 | <1 | 14 h 10 min |
| September | 73°F | 46°F | 59.6°F | 1.43 | 0.2 | 6 | 3 | 1 | 12 h 40 min |
| October | 58°F | 34°F | 45.9°F | 1.44 | 2.3 | 7 | <1 | 12 | 11 h |
| November | 46°F | 24°F | 34.8°F | 0.69 | 3.9 | 6 | <1 | 23 | 9 h 30 min |
| December | 37°F | 15°F | 26.0°F | 0.56 | 6.2 | 6 | <1 | 29 | 8 h 40 min |
| Year (annual) | 58°F | 34°F | 46.1°F | 16.40 | 36.6 | 90 | 24 | 162 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 2°C | −10°C | −4.1°C | 17 mm | 19 cm |
| February | 3°C | −9°C | −3.3°C | 18 mm | 19 cm |
| March | 8°C | −5°C | 1.9°C | 24 mm | 14 cm |
| April | 13°C | 0°C | 6.5°C | 49 mm | 8 cm |
| May | 18°C | 5°C | 11.9°C | 80 mm | 1 cm |
| June | 24°C | 10°C | 17.2°C | 63 mm | 0 cm |
| July | 29°C | 14°C | 21.7°C | 36 mm | 0 cm |
| August | 29°C | 13°C | 20.9°C | 26 mm | 0 cm |
| September | 23°C | 8°C | 15.3°C | 36 mm | 1 cm |
| October | 15°C | 1°C | 7.7°C | 37 mm | 6 cm |
| November | 8°C | −5°C | 1.6°C | 18 mm | 10 cm |
| December | 3°C | −9°C | −3.3°C | 14 mm | 16 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00241905; 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 Colstrip?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, August has the fewest days with rain (6).
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 USC00241905.
When is the last frost in Colstrip?
In Colstrip, 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 30 in half of years and before September 15 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 2
- First autumn frost, half of years before
- September 301 year in 10 before September 15; 9 in 10 before October 14
NOAA puts the median frost-free season at 138 days, and the season without a hard freeze (28°F) at 159 days.
A hard freeze (28°F) comes after May 3 in half of springs and before October 10 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Colstrip in zone 5a in ZIP code 59323, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Colstrip's NOAA station is in zone 4b: the coldest night of a typical year reaches −20°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 USC00241905; 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 Colstrip?
In a normal year in Colstrip, 24 days a year reach 90°F (1 of them 100°F or more), 162 nights fall to 32°F or colder and 90 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
- 162a normal year
- Days that stay below freezing
- 42high of 32°F or less
- Days with 0.01 inch of precipitation
- 90a normal year
- Days with 1 inch of snow or more
- 18a normal year
The highest temperature in this station's record (since 1927) is 111°F, on August 6, 1961; the lowest is −42°F, on January 17, 1930.
The wettest calendar year on that record is 2016, with 25.04 in; the snowiest season is 2017–18, with 92.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00241905; records: ACIS (NOAA Regional Climate Centers), station USC00241905. Records use complete months only; a month missing more than three days is left out.
How sunny is Colstrip?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Colstrip, 4.2 kWh per square metre a day. July is the sunniest month (89%) and April the cloudiest (70%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 75% | 1.8 |
| February | 77% | 2.8 |
| March | 73% | 3.9 |
| April | 70% | 4.9 |
| May | 72% | 5.9 |
| June | 80% | 6.9 |
| July | 89% | 7.3 |
| August | 86% | 6.1 |
| September | 81% | 4.6 |
| October | 73% | 2.9 |
| November | 73% | 1.9 |
| December | 70% | 1.4 |
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 Colstrip need?
A normal year in Colstrip brings 7,369 heating degree days, 37% more than the median U.S. place (5,373), and 510 cooling degree days, 44% 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 2,267 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,251 | 0 |
| February | 1,089 | 0 |
| March | 915 | 0 |
| April | 641 | 0 |
| May | 368 | 8 |
| June | 123 | 59 |
| July | 24 | 213 |
| August | 40 | 183 |
| September | 207 | 44 |
| October | 595 | 3 |
| November | 908 | 0 |
| December | 1,210 | 0 |
| Year (annual) | 7,369 | 510 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00241905. 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 Colstrip been warmer than normal lately?
Over 71 complete years from 1929 to 2020, the station's annual mean temperature rose at a fitted 3.0°F per century (+0.17°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 Colstrip's climate compare?
Colstrip is warmer than 113 of the other 140 places with their own NOAA record in Montana, and wetter than 96. Across the 7,247 U.S. stations with normals, its annual mean of 46.1°F is warmer than 24%.
In the Köppen classification computed from these normals, Colstrip is Dfb: continental, no dry season, warm 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 Colstrip's climate
What is the coldest month in Colstrip?
January, with a normal high of 36°F and a normal low of 14°F. The warmest is July (85°F by day, 57°F at night).
Does it snow in Colstrip?
Yes: 37 inches in a normal year, falling on 24 days with 0.1 inch or more, the most in January (7.4 inches).
What is the rainiest month in Colstrip?
May, with 3.14 in of precipitation in a normal year; the driest is December with 0.56 in.
What plant hardiness zone is Colstrip in?
The USDA's 2023 map puts Colstrip in zone 5a in ZIP code 59323, the nearest ZIP area. By the same method at Colstrip's NOAA station, the coldest night of a typical year reaches −20°F (27 years, 1991-2020): zone 4b.
How late can frost come in Colstrip?
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
- Brandenberg, MT20 miles from this station, 46.6°F a year
- Hysham (25 mi SSE), MT24 miles from this station, 44.6°F a year
- Forsyth, MT26 miles from this station, 46.7°F a year
- Busby, MT29 miles from this station, 45.0°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made