Libby Dam (Base), Montana climate: Climate normals at a NOAA weather station
Libby Dam (Base)'s normal year runs from 22°F January nights to 85°F July afternoons, with 17.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.0°C, January lows of −6°C, July highs of 30°C, 433 mm of precipitation a year.
- NOAA stationLibby Dam (Base)
- Station IDUSC00245011
- Location48.41°N 115.32°W
- Elevation2,110 ft (643 m)
On October 22, the normal high in Libby Dam (Base) is 54°F and the normal low 32°F, and the chance of measurable rain or snow is 40%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Libby Dam (Base).
- Jan 35° 22°
- Feb 40° 22°
- Mar 49° 26°
- Apr 58° 32°
- May 68° 39°
- Jun 75° 46°
- Jul 85° 50°
- Aug 85° 49°
- Sep 74° 42°
- Oct 57° 34°
- Nov 42° 28°
- Dec 34° 23°
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 Libby Dam (Base) each month?
July is the warmest month, with normal highs of 85°F; January the coldest, with normal lows of 22°F. The most precipitation falls in June (2.39 in), the least in August (0.70 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 35°F | 22°F | 28.1°F | 1.50 | 14 | <1 | 30 | 8 h 40 min |
| February | 40°F | 22°F | 30.6°F | 1.15 | 11 | <1 | 27 | 10 h 10 min |
| March | 49°F | 26°F | 37.4°F | 1.09 | 11 | <1 | 28 | 11 h 50 min |
| April | 58°F | 32°F | 44.7°F | 1.23 | 11 | <1 | 19 | 13 h 40 min |
| May | 68°F | 39°F | 53.9°F | 1.75 | 12 | <1 | 6 | 15 h 10 min |
| June | 75°F | 46°F | 60.4°F | 2.39 | 12 | 2 | <1 | 16 h |
| July | 85°F | 50°F | 67.8°F | 0.85 | 6 | 11 | <1 | 15 h 40 min |
| August | 85°F | 49°F | 67.3°F | 0.70 | 5 | 10 | <1 | 14 h 20 min |
| September | 74°F | 42°F | 58.0°F | 1.12 | 8 | 1 | 2 | 12 h 40 min |
| October | 57°F | 34°F | 45.4°F | 1.72 | 12 | <1 | 14 | 11 h |
| November | 42°F | 28°F | 34.9°F | 1.84 | 14 | <1 | 24 | 9 h 20 min |
| December | 34°F | 23°F | 28.4°F | 1.71 | 15 | <1 | 29 | 8 h 20 min |
| Year (annual) | 59°F | 34°F | 46.4°F | 17.05 | 132 | 24 | 178 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 1°C | −6°C | −2.2°C | 38 mm |
| February | 4°C | −6°C | −0.8°C | 29 mm |
| March | 9°C | −3°C | 3.0°C | 28 mm |
| April | 14°C | 0°C | 7.1°C | 31 mm |
| May | 20°C | 4°C | 12.2°C | 44 mm |
| June | 24°C | 8°C | 15.8°C | 61 mm |
| July | 30°C | 10°C | 19.9°C | 22 mm |
| August | 30°C | 10°C | 19.6°C | 18 mm |
| September | 23°C | 6°C | 14.4°C | 28 mm |
| October | 14°C | 1°C | 7.4°C | 44 mm |
| November | 6°C | −2°C | 1.6°C | 47 mm |
| December | 1°C | −5°C | −2.0°C | 43 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Libby 1 NE Ranger Station (10 miles away), gets 48 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00245011; 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 Libby Dam (Base)?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September has the fewest days with rain (8).
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 USC00245011.
When is the last frost at Libby Dam (Base)?
In Libby Dam (Base), the last spring frost (32°F) comes after May 11 in half of years and after May 27 in one year in ten; the first autumn frost comes before October 1 in half of years and before September 14 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 111 year in 10 after May 27; 9 in 10 after April 30
- First autumn frost, half of years before
- October 11 year in 10 before September 14; 9 in 10 before October 18
NOAA puts the median frost-free season at 142 days, and the season without a hard freeze (28°F) at 170 days.
A hard freeze (28°F) comes after April 28 in half of springs and before October 16 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Libby Dam (Base) in zone 6a in ZIP code 59923, 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 6b: the coldest night of a typical year reaches −5°F (27 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 USC00245011; 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 Libby Dam (Base)?
In a normal year in Libby Dam (Base), 24 days a year reach 90°F (1 of them 100°F or more), 178 nights fall to 32°F or colder and 132 days bring measurable precipitation.
- Days at 90°F or more
- 24a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 178a normal year
- Days that stay below freezing
- 31high of 32°F or less
- Days with 0.01 inch of precipitation
- 132a normal year
The highest temperature in this station's record (since 1986) is 108°F, on August 11, 2018; the lowest is −27°F, on January 14, 2024.
The wettest calendar year on that record is 1995, with 25.03 in; the snowiest season is 2007–08, with 55.4 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00245011; records: ACIS (NOAA Regional Climate Centers), station USC00245011. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Libby Dam (Base)?
Over a year 70% of the sunlight that would reach the ground under clear skies gets through the clouds at Libby Dam (Base), 3.6 kWh per square metre a day. July is the sunniest month (85%) and December the cloudiest (50%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 54% | 1.1 |
| February | 62% | 2.0 |
| March | 62% | 3.1 |
| April | 65% | 4.4 |
| May | 68% | 5.5 |
| June | 69% | 6.0 |
| July | 85% | 7.1 |
| August | 83% | 5.8 |
| September | 75% | 4.0 |
| October | 65% | 2.4 |
| November | 53% | 1.2 |
| December | 50% | 0.8 |
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 Libby Dam (Base) record?
A normal year at Libby Dam (Base) brings 7,046 heating degree days, 31% more than the median U.S. place (5,373), and 292 cooling degree days, 68% 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 1,864 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,145 | 0 |
| February | 965 | 0 |
| March | 856 | 0 |
| April | 608 | 0 |
| May | 349 | 4 |
| June | 167 | 27 |
| July | 43 | 130 |
| August | 46 | 117 |
| September | 225 | 15 |
| October | 606 | 0 |
| November | 903 | 0 |
| December | 1,135 | 0 |
| Year (annual) | 7,046 | 292 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00245011. 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 Libby Dam (Base) been warmer than normal?
2025 averaged 48.8°F, 2.4°F above the 1991-2020 normal of 46.4°F. 3 of the 4 complete years since 2022 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2022 | 46.0°F | −0.4°F | 19.05 |
| 2023 | 48.1°F | +1.7°F | 13.76 |
| 2024 | 47.6°F | +1.2°F | 18.56 |
| 2025 | 48.8°F | +2.4°F | 22.30 |
Over 31 complete years from 1989 to 2025, the station's annual mean temperature rose at a fitted 5.3°F per century (+0.30°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00245011; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Libby Dam (Base)'s climate compare?
Libby Dam (Base) is warmer than 121 of the 141 places with their own NOAA record in Montana, and wetter than 105. Across the 7,247 U.S. stations with normals, its annual mean of 46.4°F is warmer than 25%.
In the Köppen classification computed from these normals, Libby Dam (Base) 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 Libby Dam (Base)'s climate
What is the coldest month at Libby Dam (Base)?
January, with a normal high of 35°F and a normal low of 22°F. The warmest is July (85°F by day, 50°F at night).
Does it snow at Libby Dam (Base)?
Yes. NOAA publishes no 1991-2020 snowfall normal for the station; the nearest record that keeps one, Libby 1 NE Ranger Station (10 miles away), records 48 inches of snow in a normal year.
What is the rainiest month at Libby Dam (Base)?
June, with 2.39 in of precipitation in a normal year; the driest is August with 0.70 in.
What plant hardiness zone is Libby Dam (Base) in?
The USDA's 2023 map puts Libby Dam (Base) in zone 6a in ZIP code 59923, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −5°F (27 years, 1991-2020): zone 6b.
How late can frost come at Libby Dam (Base)?
In half of years the last 32°F night comes after May 11; 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
- Libby, MT11 miles from this station, 45.4°F a year
- Troy, MT27 miles from this station, 46.8°F a year
- Libby (32 mi SSE), MT32 miles from this station, 40.2°F a year
- Fortine, MT32 miles from this station, 43.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made