Big Sandy, Montana climate: Normal weather by month, frost dates and records
Big Sandy's normal year runs from 10°F January nights to 86°F July afternoons, with 13.3 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.3°C, January lows of −12°C, July highs of 30°C, 337 mm of precipitation a year.
- NOAA stationBig Sandy
- Station IDUSC00240770
- Location48.13°N 110.06°W
- Elevation2,770 ft (844 m)
- Population604
On October 23, the normal high in Big Sandy is 55°F and the normal low 29°F, and the chance of measurable rain or snow is 12%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Big Sandy.
- Jan 31° 10°
- Feb 35° 13°
- Mar 46° 22°
- Apr 58° 33°
- May 68° 41°
- Jun 76° 49°
- Jul 86° 55°
- Aug 85° 53°
- Sep 74° 44°
- Oct 59° 33°
- Nov 44° 22°
- Dec 34° 13°
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 Big Sandy each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 10°F. The most precipitation falls in June (3.12 in), the least in February (0.39 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 31°F | 10°F | 20.3°F | 0.45 | 3 | <1 | 29 | 8 h 50 min |
| February | 35°F | 13°F | 24.3°F | 0.39 | 2 | <1 | 26 | 10 h 10 min |
| March | 46°F | 22°F | 34.0°F | 0.47 | 3 | <1 | 27 | 11 h 50 min |
| April | 58°F | 33°F | 45.5°F | 1.27 | 5 | <1 | 17 | 13 h 40 min |
| May | 68°F | 41°F | 54.6°F | 2.07 | 7 | <1 | 6 | 15 h 10 min |
| June | 76°F | 49°F | 62.4°F | 3.12 | 9 | 2 | 1 | 16 h |
| July | 86°F | 55°F | 70.3°F | 1.40 | 5 | 12 | <1 | 15 h 40 min |
| August | 85°F | 53°F | 69.1°F | 0.99 | 4 | 11 | <1 | 14 h 20 min |
| September | 74°F | 44°F | 59.0°F | 1.16 | 4 | 3 | 2 | 12 h 40 min |
| October | 59°F | 33°F | 45.6°F | 0.93 | 4 | <1 | 16 | 11 h |
| November | 44°F | 22°F | 32.6°F | 0.60 | 3 | <1 | 25 | 9 h 20 min |
| December | 34°F | 13°F | 23.3°F | 0.43 | 2 | <1 | 29 | 8 h 20 min |
| Year (annual) | 58°F | 32°F | 45.1°F | 13.28 | 50 | 28 | 180 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −1°C | −12°C | −6.5°C | 11 mm |
| February | 2°C | −10°C | −4.3°C | 10 mm |
| March | 8°C | −6°C | 1.1°C | 12 mm |
| April | 15°C | 0°C | 7.5°C | 32 mm |
| May | 20°C | 5°C | 12.6°C | 53 mm |
| June | 24°C | 9°C | 16.9°C | 79 mm |
| July | 30°C | 13°C | 21.3°C | 36 mm |
| August | 29°C | 12°C | 20.6°C | 25 mm |
| September | 23°C | 7°C | 15.0°C | 29 mm |
| October | 15°C | 0°C | 7.6°C | 24 mm |
| November | 6°C | −6°C | 0.3°C | 15 mm |
| December | 1°C | −11°C | −4.8°C | 11 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Loma (25 miles away), gets 36 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00240770; 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 Big Sandy?
Normal highs sit between 65°F and 85°F in May, June, August and September. Of those, August has the fewest days with rain (4).
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 USC00240770.
When is the last frost in Big Sandy?
In Big Sandy, the last spring frost (32°F) comes after May 17 in half of years and after June 4 in one year in ten; the first autumn frost comes before September 25 in half of years and before September 12 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 171 year in 10 after June 4; 9 in 10 after May 4
- First autumn frost, half of years before
- September 251 year in 10 before September 12; 9 in 10 before October 7
NOAA puts the median frost-free season at 128 days, and the season without a hard freeze (28°F) at 152 days.
A hard freeze (28°F) comes after May 4 in half of springs and before October 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Big Sandy in zone 4a in ZIP code 59521, the nearest ZIP area.
Frost dates for every NOAA station in Montana · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00240770; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 Big Sandy?
In a normal year in Big Sandy, 28 days a year reach 90°F (2 of them 100°F or more), 180 nights fall to 32°F or colder and 50 days bring measurable precipitation.
- Days at 90°F or more
- 28a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 180a normal year
- Days that stay below freezing
- 47high of 32°F or less
- Days with 0.01 inch of precipitation
- 50a normal year
The highest temperature in this station's record (since 1921) is 111°F, on August 5, 1961; the lowest is −51°F, on January 25, 1969.
The wettest calendar year on that record is 1975, with 20.91 in; the snowiest season is 1937–38, with 51.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00240770; records: ACIS (NOAA Regional Climate Centers), station USC00240770. Records use complete months only; a month missing more than three days is left out.
How sunny is Big Sandy?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Big Sandy, 3.9 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (62%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 67% | 1.3 |
| February | 69% | 2.3 |
| March | 70% | 3.5 |
| April | 72% | 4.9 |
| May | 73% | 5.9 |
| June | 78% | 6.6 |
| July | 87% | 7.1 |
| August | 85% | 5.8 |
| September | 79% | 4.2 |
| October | 73% | 2.6 |
| November | 67% | 1.5 |
| December | 62% | 1.0 |
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 Big Sandy need?
A normal year in Big Sandy brings 7,690 heating degree days, 43% more than the median U.S. place (5,373), and 456 cooling degree days, 50% 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 2,205 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,386 | 0 |
| February | 1,140 | 0 |
| March | 961 | 0 |
| April | 586 | 1 |
| May | 335 | 11 |
| June | 127 | 49 |
| July | 29 | 192 |
| August | 42 | 169 |
| September | 215 | 34 |
| October | 603 | 2 |
| November | 974 | 0 |
| December | 1,294 | 0 |
| Year (annual) | 7,690 | 456 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00240770. 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 Big Sandy been warmer than normal lately?
2023 averaged 47.2°F, 2.1°F above the 1991-2020 normal of 45.1°F.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2023 | 47.2°F | +2.1°F | 7.23 |
Over 56 complete years from 1925 to 2023, the station's annual mean temperature rose at a fitted 1.2°F per century (+0.07°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00240770; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Big Sandy's climate compare?
Big Sandy is warmer than 93 of the other 140 places with their own NOAA record in Montana, and wetter than 35. Across the 7,247 U.S. stations with normals, its annual mean of 45.1°F is warmer than 20%.
In the Köppen classification computed from these normals, Big Sandy 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 Big Sandy share this climate record?
6 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.
- Rocky Boy West, MT905 people · 12 mi N
- St. Pierre, MT467 people · 13 mi NE
- Parker School, MT357 people · 17 mi NE
- Boneau, MT284 people · 14 mi NE
- Rocky Boy's Agency, MT124 people · 16 mi NE
- Box Elder, MT39 people · 13 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 Big Sandy's climate
What is the coldest month in Big Sandy?
January, with a normal high of 31°F and a normal low of 10°F. The warmest is July (86°F by day, 55°F at night).
Does it snow in Big Sandy?
Yes. NOAA publishes no 1991-2020 snowfall normal for Big Sandy's NOAA station; the nearest record that keeps one, Loma (25 miles away), records 36 inches of snow in a normal year.
What is the rainiest month in Big Sandy?
June, with 3.12 in of precipitation in a normal year; the driest is February with 0.39 in.
What plant hardiness zone is Big Sandy in?
The USDA's 2023 map puts Big Sandy in zone 4a in ZIP code 59521, the nearest ZIP area.
How late can frost come in Big Sandy?
In half of years the last 32°F night comes after May 17; in one year in ten it comes after June 4. Waiting until June 4 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Loma, MT25 miles from this station, 44.8°F a year
- Rudyard (19 mi S), MT27 miles from this station, 40.6°F a year
- Fort Assiniboine, MT28 miles from this station, 43.5°F a year
- Havre, MT31 miles from this station, 43.6°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made