Troy, Montana climate: Normal weather by month, frost dates and records
Troy's normal year runs from 23°F January nights to 87°F July afternoons, with 24.4 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.2°C, January lows of −5°C, July highs of 30°C, 620 mm of precipitation a year.
- NOAA stationTroy
- Station IDUSC00248390
- Location48.48°N 115.91°W
- Elevation1,929 ft (588 m)
- Population911
On October 22, the normal high in Troy is 52°F and the normal low 33°F, and the chance of measurable rain or snow is 33%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Troy.
- Jan 33° 23°
- Feb 39° 24°
- Mar 50° 28°
- Apr 59° 33°
- May 70° 40°
- Jun 76° 46°
- Jul 87° 49°
- Aug 86° 48°
- Sep 75° 42°
- Oct 57° 35°
- Nov 41° 29°
- Dec 32° 24°
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 Troy each month?
July is the warmest month, with normal highs of 87°F; January the coldest, with normal lows of 23°F. The most precipitation falls in November (3.50 in), the least in August (0.71 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 33°F | 23°F | 27.8°F | 2.63 | 14 | <1 | 27 | 8 h 40 min |
| February | 39°F | 24°F | 31.3°F | 1.85 | 10 | <1 | 24 | 10 h 10 min |
| March | 50°F | 28°F | 38.9°F | 2.44 | 11 | <1 | 22 | 11 h 50 min |
| April | 59°F | 33°F | 46.0°F | 1.65 | 9 | <1 | 15 | 13 h 40 min |
| May | 70°F | 40°F | 54.9°F | 1.79 | 10 | 1 | 5 | 15 h 10 min |
| June | 76°F | 46°F | 61.0°F | 2.52 | 11 | 3 | <1 | 16 h 10 min |
| July | 87°F | 49°F | 68.1°F | 0.88 | 5 | 15 | <1 | 15 h 50 min |
| August | 86°F | 48°F | 66.8°F | 0.71 | 5 | 13 | <1 | 14 h 20 min |
| September | 75°F | 42°F | 58.3°F | 1.21 | 6 | 2 | 3 | 12 h 40 min |
| October | 57°F | 35°F | 45.6°F | 2.42 | 9 | <1 | 11 | 11 h |
| November | 41°F | 29°F | 34.9°F | 3.50 | 14 | <1 | 18 | 9 h 20 min |
| December | 32°F | 24°F | 27.9°F | 2.79 | 13 | <1 | 27 | 8 h 20 min |
| Year (annual) | 59°F | 35°F | 46.8°F | 24.39 | 116 | 34 | 152 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 0°C | −5°C | −2.3°C | 67 mm |
| February | 4°C | −5°C | −0.4°C | 47 mm |
| March | 10°C | −2°C | 3.8°C | 62 mm |
| April | 15°C | 1°C | 7.8°C | 42 mm |
| May | 21°C | 5°C | 12.7°C | 45 mm |
| June | 24°C | 8°C | 16.1°C | 64 mm |
| July | 30°C | 10°C | 20.1°C | 22 mm |
| August | 30°C | 9°C | 19.3°C | 18 mm |
| September | 24°C | 5°C | 14.6°C | 31 mm |
| October | 14°C | 1°C | 7.6°C | 61 mm |
| November | 5°C | −1°C | 1.6°C | 89 mm |
| December | 0°C | −5°C | −2.3°C | 71 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Libby 1 NE Ranger Station (18 miles away), gets 48 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00248390; 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 Troy?
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 USC00248390.
When is the last frost in Troy?
In Troy, the last spring frost (32°F) comes after May 14 in half of years and after May 31 in one year in ten; the first autumn frost comes before September 25 in half of years and before September 9 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 141 year in 10 after May 31; 9 in 10 after April 29
- First autumn frost, half of years before
- September 251 year in 10 before September 9; 9 in 10 before October 9
NOAA puts the median frost-free season at 132 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 6 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Troy in zone 6a in ZIP code 59935, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Troy's NOAA station is in zone 6b: the coldest night of a typical year reaches −4°F (19 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 USC00248390; 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 Troy?
In a normal year in Troy, 34 days a year reach 90°F (5 of them 100°F or more), 152 nights fall to 32°F or colder and 116 days bring measurable precipitation.
- Days at 90°F or more
- 34a normal year
- Days at 100°F or more
- 5a normal year
- Nights at 32°F or colder
- 152a normal year
- Days that stay below freezing
- 26high of 32°F or less
- Days with 0.01 inch of precipitation
- 116a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USC00248390.
How sunny is Troy?
Over a year 70% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Troy, 3.6 kWh per square metre a day. July is the sunniest month (85%) and December the cloudiest (50%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 54% | 1.1 |
| February | 62% | 2.0 |
| March | 62% | 3.1 |
| April | 65% | 4.4 |
| May | 68% | 5.5 |
| June | 69% | 6.0 |
| July | 85% | 7.1 |
| August | 83% | 5.8 |
| September | 75% | 4.0 |
| October | 65% | 2.4 |
| November | 53% | 1.2 |
| December | 50% | 0.8 |
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 Troy need?
A normal year in Troy brings 6,898 heating degree days, 28% more than the median U.S. place (5,373), and 288 cooling degree days, 68% 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 1,931 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,153 | 0 |
| February | 944 | 0 |
| March | 811 | 0 |
| April | 569 | 0 |
| May | 317 | 5 |
| June | 152 | 32 |
| July | 34 | 129 |
| August | 49 | 107 |
| September | 217 | 16 |
| October | 603 | 0 |
| November | 902 | 0 |
| December | 1,149 | 0 |
| Year (annual) | 6,898 | 288 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00248390. 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 Troy been warmer than normal lately?
2021 averaged 49.2°F, 2.4°F above the 1991-2020 normal of 46.8°F.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 49.2°F | +2.4°F | – |
Source: observed years: ACIS, station USC00248390. A year counts only with all twelve months complete.
How does Troy's climate compare?
Troy is warmer than 126 of the other 140 places with their own NOAA record in Montana, and wetter than 124. Across the 7,247 U.S. stations with normals, its annual mean of 46.8°F is warmer than 27%.
In the Köppen classification computed from these normals, Troy is Dsb: continental, dry-summer, 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.
Questions about Troy's climate
What is the coldest month in Troy?
January, with a normal high of 33°F and a normal low of 23°F. The warmest is July (87°F by day, 49°F at night).
Does it snow in Troy?
Yes. NOAA publishes no 1991-2020 snowfall normal for Troy's NOAA station; the nearest record that keeps one, Libby 1 NE Ranger Station (18 miles away), records 48 inches of snow in a normal year.
What is the rainiest month in Troy?
November, with 3.50 in of precipitation in a normal year; the driest is August with 0.71 in.
What plant hardiness zone is Troy in?
The USDA's 2023 map puts Troy in zone 6a in ZIP code 59935, the nearest ZIP area. By the same method at Troy's NOAA station, the coldest night of a typical year reaches −4°F (19 years, 1991-2020): zone 6b.
How late can frost come in Troy?
In half of years the last 32°F night comes after May 14; in one year in ten it comes after May 31. Waiting until May 31 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Libby, MT17 miles from this station, 45.4°F a year
- Bonners Ferry, ID24 miles from this station, 47.6°F a year
- Libby Dam (Base), MT27 miles from this station, 46.4°F a year
- Heron, MT28 miles from this station, 45.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made