Harlowton, Montana climate: Normal weather by month, frost dates and records
Harlowton's normal year runs from 13°F January nights to 84°F July afternoons, with 13.2 inches of precipitation and 20 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.6°C, January lows of −10°C, July highs of 29°C, 335 mm of precipitation a year.
- NOAA stationHarlowton
- Station IDUSC00243939
- Location46.44°N 109.84°W
- Elevation4,222 ft (1,287 m)
- Population944
On October 22, the normal high in Harlowton is 54°F and the normal low 27°F, and the chance of measurable rain or snow is 14%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Harlowton.
- Jan 36° 13°
- Feb 38° 14°
- Mar 48° 20°
- Apr 54° 28°
- May 64° 37°
- Jun 74° 46°
- Jul 84° 50°
- Aug 83° 48°
- Sep 73° 40°
- Oct 57° 30°
- Nov 45° 21°
- Dec 35° 15°
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 Harlowton each month?
July is the warmest month, with normal highs of 84°F; January the coldest, with normal lows of 13°F. The most precipitation falls in June (2.81 in), the least in February (0.30 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 36°F | 13°F | 24.5°F | 0.31 | 3.7 | 4 | <1 | 29 | 9 h |
| February | 38°F | 14°F | 26.2°F | 0.30 | 1.9 | 3 | <1 | 26 | 10 h 20 min |
| March | 48°F | 20°F | 33.7°F | 0.55 | 2.6 | 5 | <1 | 28 | 11 h 50 min |
| April | 54°F | 28°F | 41.0°F | 1.34 | 3.1 | 8 | <1 | 21 | 13 h 30 min |
| May | 64°F | 37°F | 50.7°F | 2.53 | 0.3 | 9 | <1 | 9 | 15 h |
| June | 74°F | 46°F | 59.6°F | 2.81 | 0.0 | 11 | 1 | <1 | 15 h 50 min |
| July | 84°F | 50°F | 66.9°F | 1.42 | 0.0 | 8 | 9 | <1 | 15 h 30 min |
| August | 83°F | 48°F | 65.8°F | 1.25 | 0.0 | 6 | 9 | <1 | 14 h 10 min |
| September | 73°F | 40°F | 56.1°F | 1.07 | 0.1 | 5 | 2 | 4 | 12 h 40 min |
| October | 57°F | 30°F | 43.5°F | 0.68 | 0.6 | 5 | <1 | 19 | 11 h |
| November | 45°F | 21°F | 32.6°F | 0.51 | 3.6 | 4 | <1 | 26 | 9 h 30 min |
| December | 35°F | 15°F | 25.0°F | 0.41 | 3.7 | 3 | <1 | 29 | 8 h 40 min |
| Year (annual) | 58°F | 30°F | 43.8°F | 13.18 | 19.6 | 71 | 21 | 191 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 2°C | −10°C | −4.2°C | 8 mm | 9 cm |
| February | 3°C | −10°C | −3.2°C | 8 mm | 5 cm |
| March | 9°C | −7°C | 0.9°C | 14 mm | 7 cm |
| April | 12°C | −2°C | 5.0°C | 34 mm | 8 cm |
| May | 18°C | 3°C | 10.4°C | 64 mm | 1 cm |
| June | 23°C | 8°C | 15.3°C | 71 mm | 0 cm |
| July | 29°C | 10°C | 19.4°C | 36 mm | 0 cm |
| August | 28°C | 9°C | 18.8°C | 32 mm | 0 cm |
| September | 23°C | 4°C | 13.4°C | 27 mm | 0 cm |
| October | 14°C | −1°C | 6.4°C | 17 mm | 2 cm |
| November | 7°C | −6°C | 0.3°C | 13 mm | 9 cm |
| December | 2°C | −10°C | −3.9°C | 10 mm | 9 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243939; 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 Harlowton?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, September has the fewest days with rain (5).
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 USC00243939.
When is the last frost in Harlowton?
In Harlowton, the last spring frost (32°F) comes after May 23 in half of years and after June 6 in one year in ten; the first autumn frost comes before September 16 in half of years and before September 1 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 231 year in 10 after June 6; 9 in 10 after May 12
- First autumn frost, half of years before
- September 161 year in 10 before September 1; 9 in 10 before September 28
NOAA puts the median frost-free season at 113 days, and the season without a hard freeze (28°F) at 137 days.
A hard freeze (28°F) comes after May 12 in half of springs and before September 27 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Harlowton in zone 4b in ZIP code 59036, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Harlowton's NOAA station is in zone 4b: the coldest night of a typical year reaches −24°F (19 complete years).
Frost dates for every NOAA station in Montana · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00243939; 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 Harlowton?
In a normal year in Harlowton, 21 days a year reach 90°F, 191 nights fall to 32°F or colder and 71 days bring measurable precipitation.
- Days at 90°F or more
- 21a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 191a normal year
- Days that stay below freezing
- 33high of 32°F or less
- Days with 0.01 inch of precipitation
- 71a normal year
- Days with 1 inch of snow or more
- 11a normal year
The highest temperature in this station's record (since 1948) is 106°F, on July 12, 2026; the lowest is −41°F, on January 12, 2024.
The wettest calendar year on that record is 1962, with 20.56 in; the snowiest season is 1958–59, with 70.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00243939; records: ACIS (NOAA Regional Climate Centers), station USC00243939. Records use complete months only; a month missing more than three days is left out.
How sunny is Harlowton?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Harlowton, 4.0 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 72% | 1.7 |
| February | 74% | 2.6 |
| March | 71% | 3.7 |
| April | 68% | 4.8 |
| May | 71% | 5.8 |
| June | 77% | 6.7 |
| July | 87% | 7.1 |
| August | 85% | 5.9 |
| September | 79% | 4.4 |
| October | 73% | 2.8 |
| November | 71% | 1.8 |
| December | 66% | 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 Harlowton need?
A normal year in Harlowton brings 7,934 heating degree days, 48% more than the median U.S. place (5,373), and 230 cooling degree days, 75% 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 1,696 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,256 | 0 |
| February | 1,088 | 0 |
| March | 972 | 0 |
| April | 718 | 0 |
| May | 445 | 2 |
| June | 185 | 21 |
| July | 46 | 105 |
| August | 65 | 90 |
| September | 281 | 12 |
| October | 668 | 0 |
| November | 972 | 0 |
| December | 1,238 | 0 |
| Year (annual) | 7,934 | 230 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243939. 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 Harlowton been warmer than normal lately?
2025 averaged 45.3°F, 1.5°F above the 1991-2020 normal of 43.8°F. 3 of the 4 complete years since 2022 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2022 | 43.8°F | at normal | – | – |
| 2023 | 44.9°F | +1.1°F | 18.37 | 31.3 |
| 2024 | 45.3°F | +1.5°F | 10.95 | – |
| 2025 | 45.3°F | +1.5°F | – | – |
Over 51 complete years from 1951 to 2025, the station's annual mean temperature rose at a fitted 3.8°F per century (+0.21°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00243939; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Harlowton's climate compare?
Harlowton is warmer than 68 of the other 140 places with their own NOAA record in Montana, and wetter than 33. Across the 7,247 U.S. stations with normals, its annual mean of 43.8°F is warmer than 15%.
In the Köppen classification computed from these normals, Harlowton 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 Harlowton share this climate record?
3 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.
- Springwater Colony, MT35 people · 5 mi E
- Twodot, MT15 people · 11 mi W
- Duncan Ranch Colony, MT0 people · 9 mi W
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Harlowton's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Harlowton. This page uses Harlowton; the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Harlowton (11 mi NW) USC00243947 | 11 mi NW | 4,954 ft | 42.9°F | 14°F | 82°F | 16.0 | – | May 30 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Harlowton's climate
What is the coldest month in Harlowton?
January, with a normal high of 36°F and a normal low of 13°F. The warmest is July (84°F by day, 50°F at night).
Does it snow in Harlowton?
Yes: 20 inches in a normal year, falling on 14 days with 0.1 inch or more, the most in January (3.7 inches).
What is the rainiest month in Harlowton?
June, with 2.81 in of precipitation in a normal year; the driest is February with 0.30 in.
What plant hardiness zone is Harlowton in?
The USDA's 2023 map puts Harlowton in zone 4b in ZIP code 59036, the nearest ZIP area. By the same method at Harlowton's NOAA station, the coldest night of a typical year reaches −24°F (19 years, 1991-2020): zone 4b.
How late can frost come in Harlowton?
In half of years the last 32°F night comes after May 23; in one year in ten it comes after June 6. Waiting until June 6 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Judith Gap, MT17 miles from this station, 41.6°F a year
- Martinsdale, MT24 miles from this station, 43.7°F a year
- Melville (4 mi W), MT25 miles from this station, 40.4°F a year
- Ryegate, MT30 miles from this station, 46.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made