Rock Springs, Montana climate: Climate normals at a NOAA weather station
Rock Springs's normal year runs from 8°F January nights to 86°F July afternoons, with 12.6 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.8°C, January lows of −13°C, July highs of 30°C, 320 mm of precipitation a year.
- NOAA stationRock Springs
- Station IDUSC00247136
- Location46.82°N 106.25°W
- Elevation3,024 ft (922 m)
On October 23, the normal high in Rock Springs is 53°F and the normal low 29°F, and the chance of measurable rain or snow is 15%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Rock Springs.
- Jan 28° 8°
- Feb 33° 11°
- Mar 45° 21°
- Apr 56° 31°
- May 66° 40°
- Jun 77° 50°
- Jul 86° 56°
- Aug 86° 55°
- Sep 74° 45°
- Oct 57° 32°
- Nov 42° 21°
- Dec 32° 12°
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 Rock Springs each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 8°F. The most precipitation falls in May (2.70 in), the least in November (0.18 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 28°F | 8°F | 18.3°F | 0.22 | 4 | <1 | 31 | 9 h |
| February | 33°F | 11°F | 22.0°F | 0.23 | 3 | <1 | 27 | 10 h 20 min |
| March | 45°F | 21°F | 33.0°F | 0.44 | 4 | <1 | 28 | 11 h 50 min |
| April | 56°F | 31°F | 43.5°F | 1.23 | 5 | <1 | 17 | 13 h 30 min |
| May | 66°F | 40°F | 53.3°F | 2.70 | 7 | <1 | 4 | 15 h |
| June | 77°F | 50°F | 63.2°F | 2.52 | 9 | 2 | <1 | 15 h 50 min |
| July | 86°F | 56°F | 71.3°F | 1.53 | 6 | 12 | <1 | 15 h 30 min |
| August | 86°F | 55°F | 70.3°F | 1.04 | 4 | 13 | <1 | 14 h 20 min |
| September | 74°F | 45°F | 59.3°F | 1.19 | 4 | 3 | 2 | 12 h 40 min |
| October | 57°F | 32°F | 44.7°F | 1.04 | 5 | <1 | 15 | 11 h |
| November | 42°F | 21°F | 31.4°F | 0.18 | 3 | <1 | 27 | 9 h 30 min |
| December | 32°F | 12°F | 21.7°F | 0.26 | 2 | <1 | 30 | 8 h 30 min |
| Year (annual) | 57°F | 32°F | 44.3°F | 12.58 | 56 | 31 | 182 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −2°C | −13°C | −7.6°C | 6 mm |
| February | 0°C | −12°C | −5.6°C | 6 mm |
| March | 7°C | −6°C | 0.6°C | 11 mm |
| April | 13°C | −1°C | 6.4°C | 31 mm |
| May | 19°C | 5°C | 11.8°C | 69 mm |
| June | 25°C | 10°C | 17.3°C | 64 mm |
| July | 30°C | 13°C | 21.8°C | 39 mm |
| August | 30°C | 13°C | 21.3°C | 26 mm |
| September | 23°C | 7°C | 15.2°C | 30 mm |
| October | 14°C | 0°C | 7.1°C | 26 mm |
| November | 6°C | −6°C | −0.3°C | 5 mm |
| December | 0°C | −11°C | −5.7°C | 7 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Cohagen (24 miles away), gets 25 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00247136; 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 Rock Springs?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September 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 USC00247136.
When is the last frost at Rock Springs?
In Rock Springs, the last spring frost (32°F) comes after May 15 in half of years and after May 27 in one year in ten; the first autumn frost comes before September 25 in half of years and before September 10 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 27; 9 in 10 after May 2
- First autumn frost, half of years before
- September 251 year in 10 before September 10; 9 in 10 before October 6
NOAA puts the median frost-free season at 132 days, and the season without a hard freeze (28°F) at 152 days.
A hard freeze (28°F) comes after May 5 in half of springs and before October 3 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Rock Springs in zone 4a in ZIP code 59312, 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 4b: the coldest night of a typical year reaches −24°F (17 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 USC00247136; 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 Rock Springs?
In a normal year in Rock Springs, 31 days a year reach 90°F (3 of them 100°F or more), 182 nights fall to 32°F or colder and 56 days bring measurable precipitation.
- Days at 90°F or more
- 31a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 182a normal year
- Days that stay below freezing
- 53high of 32°F or less
- Days with 0.01 inch of precipitation
- 56a normal year
The highest temperature in this station's record (since 1951) is 109°F, on June 26, 2012; the lowest is −40°F, on January 20, 1954.
The wettest calendar year on that record is 1978, with 19.51 in; the snowiest season is 1958–59, with 42.7 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00247136; records: ACIS (NOAA Regional Climate Centers), station USC00247136. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Rock Springs?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds at Rock Springs, 4.1 kWh per square metre a day. July is the sunniest month (89%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 71% | 1.6 |
| February | 73% | 2.6 |
| March | 70% | 3.6 |
| April | 71% | 4.9 |
| May | 74% | 6.0 |
| June | 80% | 6.8 |
| July | 89% | 7.2 |
| August | 87% | 6.0 |
| September | 81% | 4.4 |
| October | 74% | 2.9 |
| November | 73% | 1.8 |
| December | 66% | 1.3 |
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 Rock Springs record?
A normal year at Rock Springs brings 8,037 heating degree days, 50% more than the median U.S. place (5,373), and 544 cooling degree days, 40% 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 2,254 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,446 | 0 |
| February | 1,202 | 0 |
| March | 994 | 0 |
| April | 647 | 0 |
| May | 368 | 7 |
| June | 116 | 62 |
| July | 23 | 218 |
| August | 37 | 202 |
| September | 223 | 52 |
| October | 631 | 2 |
| November | 1,008 | 0 |
| December | 1,342 | 0 |
| Year (annual) | 8,037 | 544 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00247136. 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.
How does Rock Springs's climate compare?
Rock Springs is warmer than 79 of the 141 places with their own NOAA record in Montana, and wetter than 25. Across the 7,247 U.S. stations with normals, its annual mean of 44.3°F is warmer than 17%.
In the Köppen classification computed from these normals, Rock Springs 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.
Questions about Rock Springs's climate
What is the coldest month at Rock Springs?
January, with a normal high of 28°F and a normal low of 8°F. The warmest is July (86°F by day, 56°F at night).
Does it snow at Rock Springs?
Yes. NOAA publishes no 1991-2020 snowfall normal for the station; the nearest record that keeps one, Cohagen (24 miles away), records 25 inches of snow in a normal year.
What is the rainiest month at Rock Springs?
May, with 2.70 in of precipitation in a normal year; the driest is November with 0.18 in.
What plant hardiness zone is Rock Springs in?
The USDA's 2023 map puts Rock Springs in zone 4a in ZIP code 59312, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −24°F (17 years, 1991-2020): zone 4b.
How late can frost come at Rock Springs?
In half of years the last 32°F night comes after May 15; 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
- Cohagen, MT24 miles from this station, 43.6°F a year
- Miles City, MT32 miles from this station, 46.1°F a year
- Brockway, MT38 miles from this station, 44.0°F a year
- Forsyth, MT43 miles from this station, 46.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made