Hebgen Dam, Montana climate: Climate normals at a NOAA weather station
Hebgen Dam's normal year runs from 4°F January nights to 79°F July afternoons, with 28.6 inches of precipitation and 177 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 2.8°C, January lows of −16°C, July highs of 26°C, 727 mm of precipitation a year.
- NOAA stationHebgen Dam
- Station IDUSC00244038
- Location44.87°N 111.34°W
- Elevation6,489 ft (1,978 m)
On October 23, the normal high in Hebgen Dam is 47°F and the normal low 26°F, and the chance of measurable rain or snow is 27%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Hebgen Dam.
- Jan 23° 4°
- Feb 28° 5°
- Mar 38° 14°
- Apr 47° 23°
- May 58° 32°
- Jun 68° 39°
- Jul 79° 45°
- Aug 78° 43°
- Sep 68° 37°
- Oct 51° 28°
- Nov 34° 18°
- Dec 23° 6°
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 Hebgen Dam each month?
July is the warmest month, with normal highs of 79°F; January the coldest, with normal lows of 4°F. The most precipitation falls in May (3.14 in), the least in August (1.38 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 23°F | 4°F | 13.2°F | 3.06 | 43.8 | 14 | <1 | 31 | 9 h 10 min |
| February | 28°F | 5°F | 16.5°F | 2.76 | 33.7 | 11 | <1 | 28 | 10 h 20 min |
| March | 38°F | 14°F | 26.1°F | 2.17 | 20.6 | 9 | <1 | 30 | 11 h 50 min |
| April | 47°F | 23°F | 35.0°F | 2.28 | 7.7 | 10 | <1 | 28 | 13 h 30 min |
| May | 58°F | 32°F | 45.4°F | 3.14 | 1.2 | 12 | <1 | 16 | 14 h 50 min |
| June | 68°F | 39°F | 53.7°F | 2.99 | 0.0 | 12 | <1 | 3 | 15 h 30 min |
| July | 79°F | 45°F | 61.7°F | 1.62 | 0.0 | 8 | 1 | <1 | 15 h 20 min |
| August | 78°F | 43°F | 60.7°F | 1.38 | 0.0 | 6 | <1 | 1 | 14 h 10 min |
| September | 68°F | 37°F | 52.4°F | 1.59 | 0.0 | 6 | <1 | 7 | 12 h 40 min |
| October | 51°F | 28°F | 39.4°F | 2.08 | 4.1 | 8 | <1 | 23 | 11 h |
| November | 34°F | 18°F | 26.0°F | 2.49 | 20.9 | 10 | <1 | 29 | 9 h 40 min |
| December | 23°F | 6°F | 14.3°F | 3.07 | 45.2 | 13 | <1 | 31 | 8 h 50 min |
| Year (annual) | 50°F | 25°F | 37.0°F | 28.63 | 177.2 | 118 | 2 | 226 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −5°C | −16°C | −10.4°C | 78 mm | 111 cm |
| February | −2°C | −15°C | −8.6°C | 70 mm | 86 cm |
| March | 4°C | −10°C | −3.3°C | 55 mm | 52 cm |
| April | 8°C | −5°C | 1.7°C | 58 mm | 20 cm |
| May | 15°C | 0°C | 7.4°C | 80 mm | 3 cm |
| June | 20°C | 4°C | 12.1°C | 76 mm | 0 cm |
| July | 26°C | 7°C | 16.5°C | 41 mm | 0 cm |
| August | 26°C | 6°C | 15.9°C | 35 mm | 0 cm |
| September | 20°C | 3°C | 11.3°C | 40 mm | 0 cm |
| October | 10°C | −2°C | 4.1°C | 53 mm | 10 cm |
| November | 1°C | −8°C | −3.3°C | 63 mm | 53 cm |
| December | −5°C | −15°C | −9.8°C | 78 mm | 115 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00244038; 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 Hebgen Dam?
Normal highs sit between 65°F and 85°F in 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 USC00244038.
When is the last frost at Hebgen Dam?
In Hebgen Dam, the last spring frost (32°F) comes after June 15 in half of years and after July 7 in one year in ten; the first autumn frost comes before September 10 in half of years and before August 25 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
- June 151 year in 10 after July 7; 9 in 10 after May 29
- First autumn frost, half of years before
- September 101 year in 10 before August 25; 9 in 10 before September 27
NOAA puts the median frost-free season at 87 days, and the season without a hard freeze (28°F) at 122 days.
A hard freeze (28°F) comes after May 24 in half of springs and before September 26 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Hebgen Dam in zone 4b in ZIP code 59758, 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 USC00244038; 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 at Hebgen Dam?
In a normal year in Hebgen Dam, 2 days a year reach 90°F, 226 nights fall to 32°F or colder and 118 days bring measurable precipitation.
- Days at 90°F or more
- 2a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 226a normal year
- Days that stay below freezing
- 96high of 32°F or less
- Days with 0.01 inch of precipitation
- 118a normal year
- Days with 1 inch of snow or more
- 49a normal year
The highest temperature in this station's record (since 1904) is 98°F, on July 9, 1917; the lowest is −47°F, on January 21, 1937.
The wettest calendar year on that record is 1982, with 39.57 in; the snowiest season is 1974–75, with 348.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00244038; records: ACIS (NOAA Regional Climate Centers), station USC00244038. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Hebgen Dam?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds at Hebgen Dam, 4.2 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (56%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 60% | 1.6 |
| February | 65% | 2.6 |
| March | 65% | 3.7 |
| April | 68% | 5.0 |
| May | 70% | 5.9 |
| June | 77% | 6.9 |
| July | 87% | 7.5 |
| August | 86% | 6.3 |
| September | 81% | 4.8 |
| October | 71% | 3.0 |
| November | 62% | 1.8 |
| December | 56% | 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 Hebgen Dam record?
A normal year at Hebgen Dam brings 10,200 heating degree days, 90% more than the median U.S. place (5,373), and 32 cooling degree days, 96% fewer than the median (908). Ten months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 1,017 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,606 | 0 |
| February | 1,358 | 0 |
| March | 1,206 | 0 |
| April | 899 | 0 |
| May | 609 | 0 |
| June | 342 | 1 |
| July | 123 | 19 |
| August | 144 | 11 |
| September | 377 | 1 |
| October | 792 | 0 |
| November | 1,172 | 0 |
| December | 1,573 | 0 |
| Year (annual) | 10,200 | 32 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00244038. 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.
Have recent years at Hebgen Dam been warmer than normal?
2025 averaged 40.1°F, 3.1°F above the 1991-2020 normal of 37.0°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 38.5°F | +1.5°F | – | – |
| 2022 | 35.9°F | −1.1°F | – | – |
| 2023 | 36.2°F | −0.8°F | – | – |
| 2024 | 39.4°F | +2.4°F | 24.20 | – |
| 2025 | 40.1°F | +3.1°F | – | – |
Over 75 complete years from 1914 to 2025, the station's annual mean temperature rose at a fitted 0.7°F per century (+0.04°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00244038; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Hebgen Dam's climate compare?
Hebgen Dam is warmer than 6 of the 141 places with their own NOAA record in Montana, and wetter than 129. Across the 7,247 U.S. stations with normals, its annual mean of 37.0°F is warmer than 2%.
In the Köppen classification computed from these normals, Hebgen Dam 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 Hebgen Dam's climate
What is the coldest month at Hebgen Dam?
January, with a normal high of 23°F and a normal low of 4°F. The warmest is July (79°F by day, 45°F at night).
Does it snow at Hebgen Dam?
Yes: 177 inches in a normal year, falling on 51 days with 0.1 inch or more, the most in December (45.2 inches).
What is the rainiest month at Hebgen Dam?
May, with 3.14 in of precipitation in a normal year; the driest is August with 1.38 in.
What plant hardiness zone is Hebgen Dam in?
The USDA's 2023 map puts Hebgen Dam in zone 4b in ZIP code 59758, the nearest ZIP area.
How late can frost come at Hebgen Dam?
In half of years the last 32°F night comes after June 15; in one year in ten it comes after July 7. Waiting until July 7 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- West Yellowstone, MT19 miles from this station, 35.2°F a year
- Big Sky, MT29 miles from this station, 37.7°F a year
- Lakeview, MT30 miles from this station, 36.4°F a year
- Island Park, ID31 miles from this station, 36.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made