Glasgow, Montana climate: Normal weather by month, frost dates and records
Glasgow's normal year runs from 6°F January nights to 86°F July afternoons, with 13.4 inches of precipitation and 41 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.6°C, January lows of −15°C, July highs of 30°C, 341 mm of precipitation a year.
- NOAA stationGlasgow International Airport
- Station IDUSW00094008
- Location48.21°N 106.62°W
- Elevation2,285 ft (697 m)
- Population3,169
On October 22, the normal high in Glasgow is 53°F and the normal low 31°F, and the chance of measurable rain or snow is 21%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Glasgow.
- Jan 24° 6°
- Feb 28° 9°
- Mar 42° 21°
- Apr 57° 33°
- May 68° 43°
- Jun 76° 53°
- Jul 86° 59°
- Aug 85° 57°
- Sep 73° 47°
- Oct 57° 34°
- Nov 40° 21°
- Dec 27° 10°
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 Glasgow each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 6°F. The most precipitation falls in June (2.83 in), the least in February (0.35 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 | 24°F | 6°F | 14.6°F | 0.44 | 9.8 | 8 | <1 | 31 | 8 h 50 min |
| February | 28°F | 9°F | 18.7°F | 0.35 | 6.2 | 6 | <1 | 28 | 10 h 10 min |
| March | 42°F | 21°F | 31.6°F | 0.47 | 5.6 | 7 | <1 | 28 | 11 h 50 min |
| April | 57°F | 33°F | 44.8°F | 1.01 | 2.5 | 8 | <1 | 16 | 13 h 40 min |
| May | 68°F | 43°F | 55.5°F | 2.22 | 0.9 | 11 | 1 | 4 | 15 h 10 min |
| June | 76°F | 53°F | 64.5°F | 2.83 | 0.0 | 13 | 2 | <1 | 16 h |
| July | 86°F | 59°F | 72.0°F | 1.95 | 0.0 | 9 | 10 | <1 | 15 h 40 min |
| August | 85°F | 57°F | 71.0°F | 1.27 | 0.0 | 8 | 10 | <1 | 14 h 20 min |
| September | 73°F | 47°F | 59.9°F | 1.06 | 0.0 | 7 | 3 | 1 | 12 h 40 min |
| October | 57°F | 34°F | 45.2°F | 0.92 | 1.5 | 7 | <1 | 15 | 11 h |
| November | 40°F | 21°F | 30.2°F | 0.49 | 5.9 | 6 | <1 | 27 | 9 h 20 min |
| December | 27°F | 10°F | 18.5°F | 0.43 | 8.3 | 7 | <1 | 31 | 8 h 20 min |
| Year (annual) | 55°F | 33°F | 43.9°F | 13.44 | 40.7 | 95 | 26 | 181 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −5°C | −15°C | −9.7°C | 11 mm | 25 cm |
| February | −2°C | −13°C | −7.4°C | 9 mm | 16 cm |
| March | 5°C | −6°C | −0.2°C | 12 mm | 14 cm |
| April | 14°C | 0°C | 7.1°C | 26 mm | 6 cm |
| May | 20°C | 6°C | 13.1°C | 56 mm | 2 cm |
| June | 25°C | 12°C | 18.1°C | 72 mm | 0 cm |
| July | 30°C | 15°C | 22.2°C | 50 mm | 0 cm |
| August | 29°C | 14°C | 21.7°C | 32 mm | 0 cm |
| September | 23°C | 8°C | 15.5°C | 27 mm | 0 cm |
| October | 14°C | 1°C | 7.3°C | 23 mm | 4 cm |
| November | 4°C | −6°C | −1.0°C | 12 mm | 15 cm |
| December | −3°C | −12°C | −7.5°C | 11 mm | 21 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094008; 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 Glasgow?
Normal highs sit between 65°F and 85°F in May, June, 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 USW00094008.
When is the last frost in Glasgow?
In Glasgow, the last spring frost (32°F) comes after May 6 in half of years and after May 18 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 61 year in 10 after May 18; 9 in 10 after April 24
- First autumn frost, half of years before
- September 301 year in 10 before September 17; 9 in 10 before October 13
NOAA puts the median frost-free season at 145 days, and the season without a hard freeze (28°F) at 164 days.
A hard freeze (28°F) comes after April 26 in half of springs and before October 9 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Glasgow in zone 4a in ZIP code 59230, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Glasgow's NOAA station is in zone 4a: the coldest night of a typical year reaches −28°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 USW00094008; 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 Glasgow?
In a normal year in Glasgow, 26 days a year reach 90°F (2 of them 100°F or more), 181 nights fall to 32°F or colder and 95 days bring measurable precipitation.
- Days at 90°F or more
- 26a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 181a normal year
- Days that stay below freezing
- 74high of 32°F or less
- Days with 0.01 inch of precipitation
- 95a normal year
- Days with 1 inch of snow or more
- 12a normal year
The highest temperature in Glasgow's official record (kept by the National Weather Service since 1893) is 113°F, on July 31, 1900; the lowest is −56°F, on January 12, 1916.
The wettest calendar year on that record is 2011, with 22.95 in; the snowiest season is 2010–11, with 108.6 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00094008; records: ACIS (NOAA Regional Climate Centers), NWS threaded record GGWthr. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Glasgow, and how clear are its skies?
The summer (June-August) dew point averages 48°F. The muggiest month is June, with an average dew point of 50°F; the driest air comes in December (8°F). April is the windiest month (12.2 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 | 11°F | 79% | 68% | 9.3 mph | 60% | 29% |
| February | 13°F | 74% | 60% | 10.1 mph | 55% | 35% |
| March | 24°F | 60% | 38% | 11.8 mph | 59% | 27% |
| April | 32°F | 52% | 33% | 12.2 mph | 57% | 26% |
| May | 44°F | 57% | 38% | 11.7 mph | 60% | 22% |
| June | 50°F | 55% | 34% | 10.5 mph | 75% | 12% |
| July | 50°F | 48% | 27% | 10.3 mph | 83% | 6% |
| August | 44°F | 47% | 27% | 10.5 mph | 79% | 10% |
| September | 36°F | 55% | 34% | 10.4 mph | 72% | 17% |
| October | 26°F | 66% | 45% | 10.5 mph | 62% | 28% |
| November | 16°F | 76% | 65% | 9.4 mph | 57% | 34% |
| December | 8°F | 78% | 70% | 9.0 mph | 58% | 31% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00094008. 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 Glasgow?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Glasgow, 4.0 kWh per square metre a day. July is the sunniest month (86%) and December the cloudiest (68%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 75% | 1.5 |
| February | 78% | 2.6 |
| March | 75% | 3.8 |
| April | 73% | 4.9 |
| May | 75% | 6.0 |
| June | 77% | 6.5 |
| July | 86% | 6.9 |
| August | 85% | 5.7 |
| September | 79% | 4.2 |
| October | 75% | 2.7 |
| November | 72% | 1.6 |
| December | 68% | 1.1 |
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 Glasgow need?
A normal year in Glasgow brings 8,245 heating degree days, 53% more than the median U.S. place (5,373), and 586 cooling degree days, 35% 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 2,415 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,561 | 0 |
| February | 1,296 | 0 |
| March | 1,036 | 0 |
| April | 607 | 1 |
| May | 310 | 16 |
| June | 88 | 73 |
| July | 14 | 231 |
| August | 30 | 216 |
| September | 200 | 47 |
| October | 618 | 3 |
| November | 1,043 | 0 |
| December | 1,443 | 0 |
| Year (annual) | 8,245 | 586 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094008. 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 Glasgow been warmer than normal lately?
2025 averaged 44.8°F, 0.9°F above the 1991-2020 normal of 43.9°F. 5 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 46.7°F | +2.8°F | 6.62 | 23.2 |
| 2022 | 44.2°F | +0.3°F | 10.84 | 51.2 |
| 2023 | 45.6°F | +1.7°F | 12.57 | 46.5 |
| 2024 | 46.8°F | +2.9°F | 12.10 | 32.6 |
| 2025 | 44.8°F | +0.9°F | 13.46 | 41.0 |
Over 119 complete years from 1894 to 2025, the station's annual mean temperature rose at a fitted 3.3°F per century (+0.18°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00094008; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Glasgow's climate compare?
Glasgow is warmer than 71 of the other 140 places with their own NOAA record in Montana, and wetter than 41. Across the 7,247 U.S. stations with normals, its annual mean of 43.9°F is warmer than 15%.
In the Köppen classification computed from these normals, Glasgow 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.
What do Glasgow's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Glasgow. This page uses Glasgow International Airport; the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Glasgow #2 USC00243557 | 2 mi SW | 2,090 ft | 44.2°F | 4°F | 87°F | – | – | May 3 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Glasgow's climate
What is the coldest month in Glasgow?
January, with a normal high of 24°F and a normal low of 6°F. The warmest is July (86°F by day, 59°F at night).
Does it snow in Glasgow?
Yes: 41 inches in a normal year, falling on 36 days with 0.1 inch or more, the most in January (9.8 inches).
What is the rainiest month in Glasgow?
June, with 2.83 in of precipitation in a normal year; the driest is February with 0.35 in.
What plant hardiness zone is Glasgow in?
The USDA's 2023 map puts Glasgow in zone 4a in ZIP code 59230, the nearest ZIP area. By the same method at Glasgow's NOAA station, the coldest night of a typical year reaches −28°F (30 years, 1991-2020): zone 4a.
How late can frost come in Glasgow?
In half of years the last 32°F night comes after May 6; in one year in ten it comes after May 18. Waiting until May 18 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Glasgow in OctoberThis month day by day, its records and recent years
- Montana climateThe statewide normals and every place in the state
- Nashua, MT14 miles from this station, 44.3°F a year
- St. Marie, MT14 miles from this station, 43.0°F a year
- Fort Peck, MT17 miles from this station, 46.5°F a year
- Hinsdale, MT26 miles from this station, 42.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made