Lewistown (42 mi WSW), Montana climate: Climate normals at a NOAA weather station
Lewistown (42 mi WSW)'s normal year runs from 12°F February nights to 78°F July afternoons, with 16.8 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 4.8°C, February lows of −11°C, July highs of 25°C, 426 mm of precipitation a year.
- NOAA stationLewistown (42 mi WSW)
- Station IDUSW00004140
- Location46.88°N 110.29°W
- Elevation5,070 ft (1,545 m)
On October 14, the normal high in Lewistown (42 mi WSW) is 54°F and the normal low 28°F, and the chance of measurable rain or snow is 29%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Lewistown (42 mi WSW).
- Jan 37° 13°
- Feb 36° 12°
- Mar 44° 20°
- Apr 50° 25°
- May 60° 33°
- Jun 67° 40°
- Jul 78° 44°
- Aug 77° 44°
- Sep 69° 36°
- Oct 53° 28°
- Nov 42° 20°
- Dec 35° 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 at Lewistown (42 mi WSW) each month?
July is the warmest month, with normal highs of 78°F; February the coldest, with normal lows of 12°F. The most precipitation falls in June (3.07 in), the least in December (0.55 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 37°F | 13°F | 24.9°F | 0.61 | 9 | <1 | 29 | 8 h 50 min |
| February | 36°F | 12°F | 24.0°F | 0.82 | 10 | <1 | 27 | 10 h 20 min |
| March | 44°F | 20°F | 31.5°F | 0.86 | 10 | <1 | 28 | 11 h 50 min |
| April | 50°F | 25°F | 37.3°F | 1.60 | 13 | <1 | 26 | 13 h 30 min |
| May | 60°F | 33°F | 46.3°F | 2.83 | 15 | <1 | 15 | 15 h |
| June | 67°F | 40°F | 53.7°F | 3.07 | 12 | <1 | 3 | 15 h 50 min |
| July | 78°F | 44°F | 60.9°F | 1.70 | 9 | 2 | <1 | 15 h 30 min |
| August | 77°F | 44°F | 60.6°F | 1.40 | 9 | 2 | 1 | 14 h 20 min |
| September | 69°F | 36°F | 52.2°F | 1.34 | 7 | <1 | 8 | 12 h 40 min |
| October | 53°F | 28°F | 40.6°F | 1.33 | 9 | <1 | 21 | 11 h |
| November | 42°F | 20°F | 31.2°F | 0.65 | 8 | <1 | 24 | 9 h 30 min |
| December | 35°F | 13°F | 24.0°F | 0.55 | 9 | <1 | 29 | 8 h 30 min |
| Year (annual) | 54°F | 27°F | 40.6°F | 16.76 | 120 | 4 | 212 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 3°C | −10°C | −3.9°C | 15 mm |
| February | 2°C | −11°C | −4.4°C | 21 mm |
| March | 6°C | −7°C | −0.3°C | 22 mm |
| April | 10°C | −4°C | 2.9°C | 41 mm |
| May | 15°C | 1°C | 7.9°C | 72 mm |
| June | 20°C | 4°C | 12.1°C | 78 mm |
| July | 25°C | 7°C | 16.1°C | 43 mm |
| August | 25°C | 7°C | 15.9°C | 36 mm |
| September | 20°C | 2°C | 11.2°C | 34 mm |
| October | 12°C | −2°C | 4.8°C | 34 mm |
| November | 6°C | −6°C | −0.4°C | 17 mm |
| December | 2°C | −10°C | −4.4°C | 14 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Moccasin (20 miles away), gets 45 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00004140; 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 Lewistown (42 mi WSW)?
Normal highs sit between 65°F and 85°F in 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 USW00004140.
When is the last frost at Lewistown (42 mi WSW)?
In Lewistown (42 mi WSW), the last spring frost (32°F) comes after June 15 in half of years and after July 8 in one year in ten; the first autumn frost comes before September 4 in half of years and before August 19 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 8; 9 in 10 after May 31
- First autumn frost, half of years before
- September 41 year in 10 before August 19; 9 in 10 before September 18
NOAA puts the median frost-free season at 77 days, and the season without a hard freeze (28°F) at 111 days.
A hard freeze (28°F) comes after May 25 in half of springs and before September 18 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Lewistown (42 mi WSW) in zone 4b in ZIP code 59479, 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 USW00004140; 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 Lewistown (42 mi WSW)?
In a normal year in Lewistown (42 mi WSW), 4 days a year reach 90°F, 212 nights fall to 32°F or colder and 120 days bring measurable precipitation.
- Days at 90°F or more
- 4a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 212a normal year
- Days that stay below freezing
- 49high of 32°F or less
- Days with 0.01 inch of precipitation
- 120a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USW00004140.
How sunny is it at Lewistown (42 mi WSW)?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds at Lewistown (42 mi WSW), 4.0 kWh per square metre a day. July is the sunniest month (85%) and December the cloudiest (64%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 73% | 1.7 |
| February | 76% | 2.8 |
| March | 72% | 3.9 |
| April | 68% | 4.8 |
| May | 69% | 5.7 |
| June | 74% | 6.5 |
| July | 85% | 7.2 |
| August | 84% | 6.0 |
| September | 78% | 4.4 |
| October | 71% | 2.8 |
| November | 66% | 1.7 |
| December | 64% | 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 Lewistown (42 mi WSW) record?
A normal year at Lewistown (42 mi WSW) brings 8,917 heating degree days, 66% more than the median U.S. place (5,373), and 46 cooling degree days, 95% 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 1,040 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,243 | 0 |
| February | 1,149 | 0 |
| March | 1,037 | 0 |
| April | 832 | 0 |
| May | 581 | 0 |
| June | 340 | 1 |
| July | 147 | 19 |
| August | 158 | 20 |
| September | 387 | 5 |
| October | 758 | 1 |
| November | 1,013 | 0 |
| December | 1,271 | 0 |
| Year (annual) | 8,917 | 46 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00004140. 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 Lewistown (42 mi WSW) been warmer than normal?
2025 averaged 41.8°F, 1.2°F above the 1991-2020 normal of 40.6°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 41.1°F | +0.5°F | 12.16 |
| 2022 | 39.9°F | −0.7°F | 17.70 |
| 2023 | 41.0°F | +0.4°F | 20.56 |
| 2024 | 41.9°F | +1.3°F | 16.76 |
| 2025 | 41.8°F | +1.2°F | 17.70 |
Source: observed years: ACIS, station USW00004140. A year counts only with all twelve months complete.
How does Lewistown (42 mi WSW)'s climate compare?
Lewistown (42 mi WSW) is warmer than 19 of the 141 places with their own NOAA record in Montana, and wetter than 101. Across the 7,247 U.S. stations with normals, its annual mean of 40.6°F is warmer than 7%.
In the Köppen classification computed from these normals, Lewistown (42 mi WSW) 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.
Which places near Lewistown (42 mi WSW) share this climate record?
Sapphire Ridge 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.
- Sapphire Ridge, MT17 people · 2 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 Lewistown (42 mi WSW)'s climate
What is the coldest month at Lewistown (42 mi WSW)?
February, with a normal high of 36°F and a normal low of 12°F. The warmest is July (78°F by day, 44°F at night).
Does it snow at Lewistown (42 mi WSW)?
Yes. NOAA publishes no 1991-2020 snowfall normal for the station; the nearest record that keeps one, Moccasin (20 miles away), records 45 inches of snow in a normal year.
What is the rainiest month at Lewistown (42 mi WSW)?
June, with 3.07 in of precipitation in a normal year; the driest is December with 0.55 in.
What plant hardiness zone is Lewistown (42 mi WSW) in?
The USDA's 2023 map puts Lewistown (42 mi WSW) in zone 4b in ZIP code 59479, the nearest ZIP area.
How late can frost come at Lewistown (42 mi WSW)?
In half of years the last 32°F night comes after June 15; in one year in ten it comes after July 8. Waiting until July 8 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Stanford, MT19 miles from this station, 44.6°F a year
- Moccasin, MT20 miles from this station, 43.5°F a year
- Neihart, MT25 miles from this station, 43.7°F a year
- Martinsdale, MT27 miles from this station, 43.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made