Forsyth, Montana climate: Normal weather by month, frost dates and records
Forsyth's normal year runs from 10°F January nights to 88°F July afternoons, with 16.0 inches of precipitation and 35 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.2°C, January lows of −12°C, July highs of 31°C, 406 mm of precipitation a year.
- NOAA stationForsyth
- Station IDUSC00243098
- Location46.27°N 106.68°W
- Elevation2,515 ft (767 m)
- Population1,643
On October 23, the normal high in Forsyth is 56°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 Forsyth.
- Jan 34° 10°
- Feb 38° 14°
- Mar 49° 23°
- Apr 59° 33°
- May 69° 43°
- Jun 79° 52°
- Jul 88° 58°
- Aug 87° 56°
- Sep 75° 46°
- Oct 60° 34°
- Nov 46° 22°
- 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 in Forsyth each month?
July is the warmest month, with normal highs of 88°F; January the coldest, with normal lows of 10°F. The most precipitation falls in May (2.92 in), the least in February (0.58 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 34°F | 10°F | 21.9°F | 0.61 | 7.7 | 6 | <1 | 30 | 9 h |
| February | 38°F | 14°F | 25.7°F | 0.58 | 7.3 | 6 | <1 | 27 | 10 h 20 min |
| March | 49°F | 23°F | 36.3°F | 0.94 | 3.9 | 7 | <1 | 26 | 11 h 50 min |
| April | 59°F | 33°F | 46.1°F | 1.85 | 2.8 | 8 | <1 | 14 | 13 h 30 min |
| May | 69°F | 43°F | 55.8°F | 2.92 | 0.4 | 11 | 1 | 3 | 15 h |
| June | 79°F | 52°F | 65.2°F | 2.54 | 0.0 | 10 | 4 | <1 | 15 h 50 min |
| July | 88°F | 58°F | 73.1°F | 1.38 | 0.0 | 7 | 16 | <1 | 15 h 30 min |
| August | 87°F | 56°F | 71.1°F | 1.19 | 0.0 | 6 | 14 | <1 | 14 h 10 min |
| September | 75°F | 46°F | 60.5°F | 1.38 | 0.1 | 6 | 4 | 1 | 12 h 40 min |
| October | 60°F | 34°F | 46.8°F | 1.37 | 1.5 | 7 | <1 | 13 | 11 h |
| November | 46°F | 22°F | 33.9°F | 0.66 | 4.0 | 6 | <1 | 27 | 9 h 30 min |
| December | 35°F | 13°F | 24.0°F | 0.58 | 6.9 | 5 | <1 | 31 | 8 h 40 min |
| Year (annual) | 60°F | 34°F | 46.7°F | 16.00 | 34.6 | 84 | 39 | 172 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 1°C | −12°C | −5.6°C | 15 mm | 20 cm |
| February | 3°C | −10°C | −3.5°C | 15 mm | 19 cm |
| March | 10°C | −5°C | 2.4°C | 24 mm | 10 cm |
| April | 15°C | 0°C | 7.8°C | 47 mm | 7 cm |
| May | 20°C | 6°C | 13.2°C | 74 mm | 1 cm |
| June | 26°C | 11°C | 18.4°C | 65 mm | 0 cm |
| July | 31°C | 15°C | 22.8°C | 35 mm | 0 cm |
| August | 30°C | 13°C | 21.7°C | 30 mm | 0 cm |
| September | 24°C | 8°C | 15.8°C | 35 mm | 0 cm |
| October | 16°C | 1°C | 8.2°C | 35 mm | 4 cm |
| November | 8°C | −6°C | 1.1°C | 17 mm | 10 cm |
| December | 2°C | −11°C | −4.4°C | 15 mm | 18 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243098; 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 Forsyth?
Normal highs sit between 65°F and 85°F in May, June 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 USC00243098.
When is the last frost in Forsyth?
In Forsyth, the last spring frost (32°F) comes after May 9 in half of years and after May 21 in one year in ten; the first autumn frost comes before September 29 in half of years and before September 16 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 21; 9 in 10 after April 28
- First autumn frost, half of years before
- September 291 year in 10 before September 16; 9 in 10 before October 10
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 8 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Forsyth in zone 4b in ZIP code 59327, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Forsyth's NOAA station is in zone 4b: the coldest night of a typical year reaches −24°F (30 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 USC00243098; 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 Forsyth?
In a normal year in Forsyth, 39 days a year reach 90°F (4 of them 100°F or more), 172 nights fall to 32°F or colder and 84 days bring measurable precipitation.
- Days at 90°F or more
- 39a normal year
- Days at 100°F or more
- 4a normal year
- Nights at 32°F or colder
- 172a normal year
- Days that stay below freezing
- 40high of 32°F or less
- Days with 0.01 inch of precipitation
- 84a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in this station's record (since 1975) is 112°F, on July 12, 2026; the lowest is −44°F, on December 22, 1989.
The wettest calendar year on that record is 2019, with 24.95 in; the snowiest season is 2017–18, with 93.2 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00243098; records: ACIS (NOAA Regional Climate Centers), station USC00243098. Records use complete months only; a month missing more than three days is left out.
How sunny is Forsyth?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Forsyth, 4.1 kWh per square metre a day. July is the sunniest month (89%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 71% | 1.6 |
| February | 73% | 2.6 |
| March | 70% | 3.6 |
| April | 71% | 4.9 |
| May | 74% | 6.0 |
| June | 80% | 6.8 |
| July | 89% | 7.2 |
| August | 87% | 6.0 |
| September | 81% | 4.4 |
| October | 74% | 2.9 |
| November | 73% | 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 Forsyth need?
A normal year in Forsyth brings 7,248 heating degree days, 35% more than the median U.S. place (5,373), and 619 cooling degree days, 32% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,511 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,335 | 0 |
| February | 1,099 | 0 |
| March | 890 | 0 |
| April | 569 | 1 |
| May | 298 | 13 |
| June | 78 | 86 |
| July | 9 | 260 |
| August | 24 | 215 |
| September | 179 | 44 |
| October | 564 | 2 |
| November | 933 | 0 |
| December | 1,271 | 0 |
| Year (annual) | 7,248 | 619 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00243098. 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 Forsyth been warmer than normal lately?
2025 averaged 47.8°F, 1.0°F above the 1991-2020 normal of 46.7°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 47.9°F | +1.2°F | 9.88 | 30.7 |
| 2022 | 45.8°F | −0.9°F | 14.81 | 46.8 |
| 2023 | 48.5°F | +1.8°F | 17.88 | 26.7 |
| 2024 | 48.3°F | +1.6°F | 19.34 | 28.4 |
| 2025 | 47.8°F | +1.0°F | 17.53 | 29.0 |
Over 45 complete years from 1977 to 2025, the station's annual mean temperature rose at a fitted 6.0°F per century (+0.34°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00243098; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Forsyth's climate compare?
Forsyth is warmer than 124 of the other 140 places with their own NOAA record in Montana, and wetter than 92. Across the 7,247 U.S. stations with normals, its annual mean of 46.7°F is warmer than 26%.
In the Köppen classification computed from these normals, Forsyth 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 Forsyth share this climate record?
Rosebud 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.
- Rosebud, MT53 people · 11 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 Forsyth's climate
What is the coldest month in Forsyth?
January, with a normal high of 34°F and a normal low of 10°F. The warmest is July (88°F by day, 58°F at night).
Does it snow in Forsyth?
Yes: 35 inches in a normal year, falling on 19 days with 0.1 inch or more, the most in January (7.7 inches).
What is the rainiest month in Forsyth?
May, with 2.92 in of precipitation in a normal year; the driest is February with 0.58 in.
What plant hardiness zone is Forsyth in?
The USDA's 2023 map puts Forsyth in zone 4b in ZIP code 59327, the nearest ZIP area. By the same method at Forsyth's NOAA station, the coldest night of a typical year reaches −24°F (30 years, 1991-2020): zone 4b.
How late can frost come in Forsyth?
In half of years the last 32°F night comes after May 9; in one year in ten it comes after May 21. Waiting until May 21 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Colstrip, MT26 miles from this station, 46.1°F a year
- Hysham, MT27 miles from this station, 47.2°F a year
- Ingomar (9 mi E), MT32 miles from this station, 44.2°F a year
- Hysham (25 mi SSE), MT32 miles from this station, 44.6°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made