Helena, Montana climate: Normal weather by month, frost dates and records
Helena's normal year runs from 14°F January nights to 86°F July afternoons, with 11.4 inches of precipitation and 37 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 7.5°C, January lows of −10°C, July highs of 30°C, 290 mm of precipitation a year.
- NOAA stationHelena Regional Airport
- Station IDUSW00024144
- Location46.61°N 111.96°W
- Elevation3,828 ft (1,167 m)
- From the center3 miles
- Population34,729
On October 23, the normal high in Helena is 54°F and the normal low 31°F, and the chance of measurable rain or snow is 22%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Helena.
- Jan 32° 14°
- Feb 37° 17°
- Mar 48° 25°
- Apr 57° 32°
- May 66° 42°
- Jun 75° 49°
- Jul 86° 55°
- Aug 85° 53°
- Sep 73° 45°
- Oct 58° 34°
- Nov 43° 23°
- Dec 33° 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 in Helena each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 14°F. The most precipitation falls in June (2.21 in), the least in January (0.39 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 32°F | 14°F | 23.0°F | 0.39 | 6.6 | 7 | <1 | 29 | 9 h |
| February | 37°F | 17°F | 27.2°F | 0.42 | 6.6 | 7 | <1 | 26 | 10 h 20 min |
| March | 48°F | 25°F | 36.1°F | 0.52 | 4.6 | 7 | <1 | 25 | 11 h 50 min |
| April | 57°F | 32°F | 44.5°F | 1.02 | 2.9 | 9 | <1 | 15 | 13 h 30 min |
| May | 66°F | 42°F | 53.9°F | 1.95 | 0.1 | 11 | <1 | 3 | 15 h |
| June | 75°F | 49°F | 61.7°F | 2.21 | 0.0 | 12 | 2 | <1 | 15 h 50 min |
| July | 86°F | 55°F | 70.6°F | 1.06 | 0.0 | 8 | 12 | <1 | 15 h 30 min |
| August | 85°F | 53°F | 68.8°F | 1.04 | 0.3 | 6 | 11 | <1 | 14 h 20 min |
| September | 73°F | 45°F | 58.9°F | 0.96 | 0.2 | 6 | 2 | 2 | 12 h 40 min |
| October | 58°F | 34°F | 45.5°F | 0.78 | 2.8 | 7 | <1 | 14 | 11 h |
| November | 43°F | 23°F | 32.8°F | 0.59 | 5.4 | 7 | <1 | 25 | 9 h 30 min |
| December | 33°F | 14°F | 23.4°F | 0.46 | 7.7 | 7 | <1 | 30 | 8 h 40 min |
| Year (annual) | 58°F | 33°F | 45.5°F | 11.40 | 37.2 | 91 | 27 | 170 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 0°C | −10°C | −5.0°C | 10 mm | 17 cm |
| February | 3°C | −8°C | −2.7°C | 11 mm | 17 cm |
| March | 9°C | −4°C | 2.3°C | 13 mm | 12 cm |
| April | 14°C | 0°C | 6.9°C | 26 mm | 7 cm |
| May | 19°C | 5°C | 12.2°C | 50 mm | 0 cm |
| June | 24°C | 9°C | 16.5°C | 56 mm | 0 cm |
| July | 30°C | 13°C | 21.4°C | 27 mm | 0 cm |
| August | 29°C | 12°C | 20.4°C | 26 mm | 1 cm |
| September | 23°C | 7°C | 14.9°C | 24 mm | 1 cm |
| October | 14°C | 1°C | 7.5°C | 20 mm | 7 cm |
| November | 6°C | −5°C | 0.4°C | 15 mm | 14 cm |
| December | 0°C | −10°C | −4.8°C | 12 mm | 20 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024144; 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.
When is the best weather to visit Helena?
Normal highs sit between 65°F and 85°F in May, June, 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 USW00024144.
When is the last frost in Helena?
In Helena, the last spring frost (32°F) comes after May 9 in half of years and after May 25 in one year in ten; the first autumn frost comes before September 30 in half of years and before September 17 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 91 year in 10 after May 25; 9 in 10 after April 29
- First autumn frost, half of years before
- September 301 year in 10 before September 17; 9 in 10 before October 11
NOAA puts the median frost-free season at 142 days, and the season without a hard freeze (28°F) at 162 days.
A hard freeze (28°F) comes after April 29 in half of springs and before October 7 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Helena in zone 4b in ZIP code 59601. By the map's own method, the average of each year's coldest night over 1991-2020, Helena's NOAA station is in zone 5a: the coldest night of a typical year reaches −20°F (30 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 USW00024144; 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 in Helena?
In a normal year in Helena, 27 days a year reach 90°F (1 of them 100°F or more), 170 nights fall to 32°F or colder and 91 days bring measurable precipitation.
- Days at 90°F or more
- 27a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 170a normal year
- Days that stay below freezing
- 44high of 32°F or less
- Days with 0.01 inch of precipitation
- 91a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in Helena's official record (kept by the National Weather Service since 1880) is 105°F, on July 12, 2002; the lowest is −42°F, on January 31, 1893.
The wettest calendar year on that record is 1975, with 20.94 in; the snowiest season is 1880–81, with 112.8 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00024144; records: ACIS (NOAA Regional Climate Centers), NWS threaded record HLNthr. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Helena, and how clear are its skies?
The summer (June-August) dew point averages 43°F. The muggiest month is July, with an average dew point of 44°F; the driest air comes in December (12°F). April is the windiest month (8.8 mph on average), and July has the most clear or nearly clear hours (83%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 16°F | 67% | 53% | 5.9 mph | 52% | 29% |
| February | 16°F | 61% | 45% | 6.5 mph | 50% | 30% |
| March | 24°F | 54% | 36% | 7.9 mph | 49% | 29% |
| April | 29°F | 49% | 32% | 8.8 mph | 54% | 25% |
| May | 40°F | 54% | 36% | 7.7 mph | 53% | 26% |
| June | 44°F | 46% | 28% | 7.5 mph | 75% | 10% |
| July | 44°F | 40% | 22% | 6.7 mph | 83% | 6% |
| August | 40°F | 43% | 24% | 6.4 mph | 77% | 10% |
| September | 34°F | 51% | 32% | 6.2 mph | 70% | 17% |
| October | 25°F | 60% | 42% | 6.2 mph | 58% | 26% |
| November | 17°F | 66% | 53% | 5.8 mph | 53% | 30% |
| December | 12°F | 69% | 59% | 5.1 mph | 48% | 33% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024144. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is Helena?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Helena, 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 much heating and cooling does Helena need?
A normal year in Helena brings 7,499 heating degree days, 40% more than the median U.S. place (5,373), and 434 cooling degree days, 52% 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 2,130 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,304 | 0 |
| February | 1,058 | 0 |
| March | 898 | 0 |
| April | 614 | 0 |
| May | 350 | 7 |
| June | 144 | 45 |
| July | 23 | 197 |
| August | 40 | 156 |
| September | 210 | 28 |
| October | 603 | 1 |
| November | 966 | 0 |
| December | 1,290 | 0 |
| Year (annual) | 7,499 | 434 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024144. 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.
Has Helena been warmer than normal lately?
2025 averaged 47.2°F, 1.7°F above the 1991-2020 normal of 45.5°F. 5 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 48.1°F | +2.6°F | 8.61 | 43.7 |
| 2022 | 45.7°F | +0.2°F | 11.50 | 34.1 |
| 2023 | 47.7°F | +2.2°F | 12.47 | 39.5 |
| 2024 | 48.4°F | +2.9°F | 9.81 | 47.7 |
| 2025 | 47.2°F | +1.7°F | 13.89 | 43.1 |
Over 127 complete years from 1892 to 2025, the station's annual mean temperature rose at a fitted 2.5°F per century (+0.14°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00024144; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Helena's climate compare?
Helena is warmer than 107 of the other 140 places with their own NOAA record in Montana, and wetter than 9. Across the 7,247 U.S. stations with normals, its annual mean of 45.5°F is warmer than 21%.
In the Köppen classification computed from these normals, Helena 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 Helena share this climate record?
11 places have no NOAA station with 1991-2020 normals of their 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.
- Helena Valley Southeast, MT9,533 people · 3 mi E
- Helena Valley West Central, MT8,224 people · 6 mi NW
- Helena Valley Northwest, MT5,070 people · 10 mi NW
- Helena Valley Northeast, MT4,398 people · 7 mi N
- Montana City, MT2,899 people · 6 mi S
- East Helena, MT2,239 people · 2 mi SE
- Helena West Side, MT1,584 people · 7 mi W
- Spokane Creek, MT783 people · 12 mi SE
- South Hills, MT634 people · 4 mi SW
- Unionville, MT386 people · 7 mi SW
- York, MT215 people · 13 mi NE
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 Helena's climate
What is the coldest month in Helena?
January, with a normal high of 32°F and a normal low of 14°F. The warmest is July (86°F by day, 55°F at night).
Does it snow in Helena?
Yes: 37 inches in a normal year, falling on 28 days with 0.1 inch or more, the most in December (7.7 inches).
What is the rainiest month in Helena?
June, with 2.21 in of precipitation in a normal year; the driest is January with 0.39 in.
What plant hardiness zone is Helena in?
The USDA's 2023 map puts Helena in zone 4b in ZIP code 59601. By the same method at Helena's NOAA station, the coldest night of a typical year reaches −20°F (30 years, 1991-2020): zone 5a.
How late can frost come in Helena?
In half of years the last 32°F night comes after May 9; in one year in ten it comes after May 25. Waiting until May 25 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Helena in OctoberThis month day by day, its records and recent years
- Montana climateThe statewide normals and every place in the state
- Austin (1 mi W), MT14 miles from this station, 40.3°F a year
- Tizer Gardens, MT16 miles from this station, 41.0°F a year
- Elliston, MT22 miles from this station, 40.3°F a year
- Holter Dam, MT27 miles from this station, 46.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made