Heart Mountain, Wyoming climate: Climate normals at a NOAA weather station
Heart Mountain's normal year runs from 13°F January nights to 85°F July afternoons, with 9.3 inches of precipitation and 44 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.6°C, January lows of −11°C, July highs of 29°C, 236 mm of precipitation a year.
- NOAA stationHeart Mountain
- Station IDUSC00484411
- Location44.71°N 108.96°W
- Elevation4,790 ft (1,460 m)
On October 23, the normal high in Heart Mountain is 55°F and the normal low 31°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 Heart Mountain.
- Jan 34° 13°
- Feb 38° 15°
- Mar 50° 24°
- Apr 59° 31°
- May 68° 41°
- Jun 77° 48°
- Jul 85° 54°
- Aug 83° 53°
- Sep 73° 44°
- Oct 59° 33°
- Nov 45° 22°
- Dec 34° 14°
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 Heart Mountain each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 13°F. The most precipitation falls in May (1.81 in), the least in January (0.29 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 34°F | 13°F | 23.3°F | 0.29 | 7.7 | 4 | <1 | 30 | 9 h 10 min |
| February | 38°F | 15°F | 26.4°F | 0.42 | 5.8 | 4 | <1 | 27 | 10 h 20 min |
| March | 50°F | 24°F | 37.2°F | 0.56 | 7.8 | 5 | <1 | 26 | 11 h 50 min |
| April | 59°F | 31°F | 44.9°F | 0.84 | 4.5 | 5 | <1 | 17 | 13 h 30 min |
| May | 68°F | 41°F | 54.1°F | 1.81 | 0.2 | 10 | <1 | 4 | 14 h 50 min |
| June | 77°F | 48°F | 62.4°F | 1.54 | 0.0 | 9 | 1 | <1 | 15 h 30 min |
| July | 85°F | 54°F | 69.5°F | 0.90 | 0.0 | 8 | 8 | <1 | 15 h 20 min |
| August | 83°F | 53°F | 67.6°F | 0.54 | 0.0 | 7 | 4 | <1 | 14 h 10 min |
| September | 73°F | 44°F | 58.5°F | 0.88 | 0.7 | 7 | <1 | 3 | 12 h 40 min |
| October | 59°F | 33°F | 46.0°F | 0.87 | 5.7 | 5 | <1 | 12 | 11 h |
| November | 45°F | 22°F | 33.2°F | 0.34 | 5.7 | 4 | <1 | 25 | 9 h 40 min |
| December | 34°F | 14°F | 23.7°F | 0.32 | 6.1 | 3 | <1 | 30 | 8 h 50 min |
| Year (annual) | 59°F | 33°F | 45.6°F | 9.31 | 44.2 | 70 | 14 | 173 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 1°C | −11°C | −4.8°C | 7 mm | 20 cm |
| February | 3°C | −10°C | −3.1°C | 11 mm | 15 cm |
| March | 10°C | −4°C | 2.9°C | 14 mm | 20 cm |
| April | 15°C | 0°C | 7.2°C | 21 mm | 11 cm |
| May | 20°C | 5°C | 12.3°C | 46 mm | 1 cm |
| June | 25°C | 9°C | 16.9°C | 39 mm | 0 cm |
| July | 29°C | 12°C | 20.8°C | 23 mm | 0 cm |
| August | 28°C | 11°C | 19.8°C | 14 mm | 0 cm |
| September | 23°C | 7°C | 14.7°C | 22 mm | 2 cm |
| October | 15°C | 1°C | 7.8°C | 22 mm | 14 cm |
| November | 7°C | −6°C | 0.7°C | 9 mm | 14 cm |
| December | 1°C | −10°C | −4.6°C | 8 mm | 15 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00484411; 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 Heart Mountain?
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 (7).
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 USC00484411.
When is the last frost at Heart Mountain?
In Heart Mountain, the last spring frost (32°F) comes after May 15 in half of years and after June 1 in one year in ten; the first autumn frost comes before September 25 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 151 year in 10 after June 1; 9 in 10 after May 1
- First autumn frost, half of years before
- September 251 year in 10 before September 11; 9 in 10 before October 10
NOAA puts the median frost-free season at 132 days, and the season without a hard freeze (28°F) at 156 days.
A hard freeze (28°F) comes after May 2 in half of springs and before October 6 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Heart Mountain in zone 5a in ZIP code 82440, 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 5a: the coldest night of a typical year reaches −18°F (17 complete years).
Frost dates for every NOAA station in Wyoming · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00484411; 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 Heart Mountain?
In a normal year in Heart Mountain, 14 days a year reach 90°F, 173 nights fall to 32°F or colder and 70 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
- 173a normal year
- Days that stay below freezing
- 41high of 32°F or less
- Days with 0.01 inch of precipitation
- 70a normal year
- Days with 1 inch of snow or more
- 16a normal year
The highest temperature in this station's record (since 1942) is 101°F, on June 23, 1954; the lowest is −38°F, on February 3, 1989.
The wettest calendar year on that record is 1975, with 13.37 in; the snowiest season is 1996–97, with 67.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00484411; records: ACIS (NOAA Regional Climate Centers), station USC00484411. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Heart Mountain?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds at Heart Mountain, 4.4 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (65%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 71% | 1.8 |
| February | 72% | 2.8 |
| March | 74% | 4.0 |
| April | 74% | 5.3 |
| May | 75% | 6.3 |
| June | 82% | 7.2 |
| July | 87% | 7.3 |
| August | 85% | 6.2 |
| September | 83% | 4.8 |
| October | 76% | 3.2 |
| November | 72% | 2.0 |
| December | 65% | 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 many heating and cooling degree days does Heart Mountain record?
A normal year at Heart Mountain brings 7,405 heating degree days, 38% more than the median U.S. place (5,373), and 354 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 2,099 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,293 | 0 |
| February | 1,081 | 0 |
| March | 862 | 0 |
| April | 603 | 0 |
| May | 344 | 6 |
| June | 124 | 46 |
| July | 23 | 162 |
| August | 38 | 119 |
| September | 217 | 22 |
| October | 589 | 0 |
| November | 954 | 0 |
| December | 1,279 | 0 |
| Year (annual) | 7,405 | 354 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00484411. 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 Heart Mountain's climate compare?
Heart Mountain is warmer than 49 of the 71 places with their own NOAA record in Wyoming, and wetter than 16. Across the 7,247 U.S. stations with normals, its annual mean of 45.6°F is warmer than 22%.
In the Köppen classification computed from these normals, Heart Mountain 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 Heart Mountain share this climate record?
Ralston has no NOAA station with 1991-2020 normals of its 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.
- Ralston, WY128 people · 3 mi E
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 Heart Mountain's climate
What is the coldest month at Heart Mountain?
January, with a normal high of 34°F and a normal low of 13°F. The warmest is July (85°F by day, 54°F at night).
Does it snow at Heart Mountain?
Yes: 44 inches in a normal year, falling on 20 days with 0.1 inch or more, the most in March (7.8 inches).
What is the rainiest month at Heart Mountain?
May, with 1.81 in of precipitation in a normal year; the driest is January with 0.29 in.
What plant hardiness zone is Heart Mountain in?
The USDA's 2023 map puts Heart Mountain in zone 5a in ZIP code 82440, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −18°F (17 years, 1991-2020): zone 5a.
How late can frost come at Heart Mountain?
In half of years the last 32°F night comes after May 15; in one year in ten it comes after June 1. Waiting until June 1 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Wyoming climateThe statewide normals and every place in the state
- Powell, WY11 miles from this station, 43.2°F a year
- Cody, WY16 miles from this station, 46.8°F a year
- Buffalo Bill Dam, WY17 miles from this station, 46.0°F a year
- Clark (3 mi NE), WY18 miles from this station, 44.6°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made