Grass Range, Montana climate: Normal weather by month, frost dates and records
Grass Range's normal year runs from 14°F January nights to 83°F July afternoons, with 17.9 inches of precipitation and 50 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.5°C, January lows of −10°C, July highs of 29°C, 454 mm of precipitation a year.
- NOAA stationGrass Range
- Station IDUSC00243727
- Location47.03°N 108.80°W
- Elevation3,490 ft (1,064 m)
- Population115
On October 22, the normal high in Grass Range is 56°F and the normal low 31°F, and the chance of measurable rain or snow is 20%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Grass Range.
- Jan 37° 14°
- Feb 39° 16°
- Mar 48° 23°
- Apr 57° 31°
- May 66° 40°
- Jun 74° 47°
- Jul 83° 53°
- Aug 83° 52°
- Sep 73° 44°
- Oct 59° 33°
- Nov 46° 23°
- Dec 38° 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 Grass Range each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 14°F. The most precipitation falls in May (3.39 in), the least in February (0.51 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 37°F | 14°F | 25.7°F | 0.68 | 8.7 | 6 | <1 | 29 | 8 h 50 min |
| February | 39°F | 16°F | 27.2°F | 0.51 | 7.8 | 6 | <1 | 26 | 10 h 20 min |
| March | 48°F | 23°F | 35.6°F | 0.87 | 9.2 | 7 | <1 | 26 | 11 h 50 min |
| April | 57°F | 31°F | 43.9°F | 1.85 | 4.8 | 8 | <1 | 17 | 13 h 30 min |
| May | 66°F | 40°F | 52.8°F | 3.39 | 0.9 | 12 | <1 | 6 | 15 h |
| June | 74°F | 47°F | 60.7°F | 3.22 | 0.0 | 12 | 1 | <1 | 15 h 50 min |
| July | 83°F | 53°F | 68.1°F | 1.70 | 0.0 | 9 | 7 | <1 | 15 h 30 min |
| August | 83°F | 52°F | 67.3°F | 1.67 | 0.0 | 7 | 6 | <1 | 14 h 20 min |
| September | 73°F | 44°F | 58.0°F | 1.46 | 0.1 | 6 | 1 | 2 | 12 h 40 min |
| October | 59°F | 33°F | 46.1°F | 1.25 | 3.4 | 7 | <1 | 13 | 11 h |
| November | 46°F | 23°F | 34.5°F | 0.71 | 6.4 | 5 | <1 | 24 | 9 h 20 min |
| December | 38°F | 15°F | 26.4°F | 0.55 | 8.8 | 5 | <1 | 29 | 8 h 30 min |
| Year (annual) | 59°F | 33°F | 45.5°F | 17.86 | 50.1 | 88 | 14 | 171 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 3°C | −10°C | −3.5°C | 17 mm | 22 cm |
| February | 4°C | −9°C | −2.7°C | 13 mm | 20 cm |
| March | 9°C | −5°C | 2.0°C | 22 mm | 23 cm |
| April | 14°C | −1°C | 6.6°C | 47 mm | 12 cm |
| May | 19°C | 4°C | 11.6°C | 86 mm | 2 cm |
| June | 23°C | 9°C | 15.9°C | 82 mm | 0 cm |
| July | 29°C | 12°C | 20.1°C | 43 mm | 0 cm |
| August | 28°C | 11°C | 19.6°C | 42 mm | 0 cm |
| September | 23°C | 6°C | 14.4°C | 37 mm | 0 cm |
| October | 15°C | 1°C | 7.8°C | 32 mm | 9 cm |
| November | 8°C | −5°C | 1.4°C | 18 mm | 16 cm |
| December | 3°C | −9°C | −3.1°C | 14 mm | 22 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243727; 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 Grass Range?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September 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 USC00243727.
When is the last frost in Grass Range?
In Grass Range, the last spring frost (32°F) comes after May 20 in half of years and after June 6 in one year in ten; the first autumn frost comes before September 24 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 201 year in 10 after June 6; 9 in 10 after May 6
- First autumn frost, half of years before
- September 241 year in 10 before September 11; 9 in 10 before October 5
NOAA puts the median frost-free season at 126 days, and the season without a hard freeze (28°F) at 149 days.
A hard freeze (28°F) comes after May 6 in half of springs and before October 2 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Grass Range in zone 4b in ZIP code 59032, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Grass Range's NOAA station is in zone 4b: the coldest night of a typical year reaches −23°F (28 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 USC00243727; 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 Grass Range?
In a normal year in Grass Range, 14 days a year reach 90°F, 171 nights fall to 32°F or colder and 88 days bring measurable precipitation.
- Days at 90°F or more
- 14a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 171a normal year
- Days that stay below freezing
- 37high of 32°F or less
- Days with 0.01 inch of precipitation
- 88a normal year
- Days with 1 inch of snow or more
- 20a normal year
The highest temperature in this station's record (since 1914) is 107°F, on June 27, 1936; the lowest is −44°F, on February 15, 1936.
The wettest calendar year on that record is 1962, with 25.08 in; the snowiest season is 1958–59, with 120.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00243727; records: ACIS (NOAA Regional Climate Centers), station USC00243727. Records use complete months only; a month missing more than three days is left out.
How sunny is Grass Range?
Over a year 77% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Grass Range, 4.0 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (67%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 73% | 1.6 |
| February | 75% | 2.6 |
| March | 72% | 3.7 |
| April | 70% | 4.8 |
| May | 72% | 5.8 |
| June | 77% | 6.6 |
| July | 87% | 7.1 |
| August | 85% | 5.9 |
| September | 79% | 4.3 |
| October | 73% | 2.7 |
| November | 71% | 1.7 |
| December | 67% | 1.2 |
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 Grass Range need?
A normal year in Grass Range brings 7,378 heating degree days, 37% more than the median U.S. place (5,373), and 314 cooling degree days, 65% 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 1,956 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,218 | 0 |
| February | 1,057 | 0 |
| March | 912 | 0 |
| April | 633 | 0 |
| May | 384 | 4 |
| June | 157 | 28 |
| July | 39 | 135 |
| August | 50 | 121 |
| September | 232 | 24 |
| October | 585 | 1 |
| November | 915 | 0 |
| December | 1,195 | 0 |
| Year (annual) | 7,378 | 314 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243727. 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 Grass Range been warmer than normal lately?
2025 averaged 47.6°F, 2.1°F above the 1991-2020 normal of 45.5°F. 2 of the 3 complete years since 2022 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2022 | 45.5°F | at normal | 19.39 | 58.5 |
| 2023 | 47.3°F | +1.8°F | 20.53 | – |
| 2025 | 47.6°F | +2.1°F | 18.62 | – |
Over 66 complete years from 1936 to 2025, the station's annual mean temperature rose at a fitted 3.3°F per century (+0.18°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00243727; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Grass Range's climate compare?
Grass Range is warmer than 107 of the other 140 places with their own NOAA record in Montana, and wetter than 107. Across the 7,247 U.S. stations with normals, its annual mean of 45.5°F is warmer than 21%.
In the Köppen classification computed from these normals, Grass Range 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.
Which places near Grass Range 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.
- Fords Creek Colony, MT31 people · 9 mi NW
- Ayers Ranch Colony, MT14 people · 7 mi W
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 Grass Range's climate
What is the coldest month in Grass Range?
January, with a normal high of 37°F and a normal low of 14°F. The warmest is July (83°F by day, 53°F at night).
Does it snow in Grass Range?
Yes: 50 inches in a normal year, falling on 28 days with 0.1 inch or more, the most in March (9.2 inches).
What is the rainiest month in Grass Range?
May, with 3.39 in of precipitation in a normal year; the driest is February with 0.51 in.
What plant hardiness zone is Grass Range in?
The USDA's 2023 map puts Grass Range in zone 4b in ZIP code 59032, the nearest ZIP area. By the same method at Grass Range's NOAA station, the coldest night of a typical year reaches −23°F (28 years, 1991-2020): zone 4b.
How late can frost come in Grass Range?
In half of years the last 32°F night comes after May 20; in one year in ten it comes after June 6. Waiting until June 6 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Flatwillow (4 mi ENE), MT25 miles from this station, 46.5°F a year
- Valentine, MT26 miles from this station, 43.9°F a year
- Lewistown, MT31 miles from this station, 43.1°F a year
- Roy, MT32 miles from this station, 45.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made