Joliet, Montana climate: Normal weather by month, frost dates and records
Joliet's normal year runs from 10°F January nights to 86°F July afternoons, with 14.5 inches of precipitation and 51 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.5°C, January lows of −12°C, July highs of 30°C, 369 mm of precipitation a year.
- NOAA stationJoliet
- Station IDUSC00244506
- Location45.47°N 109.01°W
- Elevation3,838 ft (1,170 m)
- From the center2 miles
- Population620
On October 22, the normal high in Joliet is 56°F and the normal low 26°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 Joliet.
- Jan 36° 10°
- Feb 39° 12°
- Mar 49° 19°
- Apr 57° 27°
- May 66° 36°
- Jun 76° 44°
- Jul 86° 50°
- Aug 84° 48°
- Sep 74° 39°
- Oct 59° 29°
- Nov 45° 19°
- Dec 36° 11°
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 Joliet each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 10°F. The most precipitation falls in May (2.67 in), the least in January (0.53 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 36°F | 10°F | 22.9°F | 0.53 | 7.7 | 5 | <1 | 29 | 9 h |
| February | 39°F | 12°F | 25.3°F | 0.57 | 9.5 | 5 | <1 | 26 | 10 h 20 min |
| March | 49°F | 19°F | 34.1°F | 0.84 | 8.0 | 6 | <1 | 27 | 11 h 50 min |
| April | 57°F | 27°F | 41.5°F | 1.89 | 4.1 | 9 | <1 | 20 | 13 h 30 min |
| May | 66°F | 36°F | 51.0°F | 2.67 | 0.8 | 11 | <1 | 7 | 14 h 50 min |
| June | 76°F | 44°F | 60.1°F | 2.11 | 0.0 | 10 | 3 | <1 | 15 h 40 min |
| July | 86°F | 50°F | 67.8°F | 0.94 | 0.0 | 7 | 12 | <1 | 15 h 20 min |
| August | 84°F | 48°F | 66.1°F | 0.88 | 0.0 | 6 | 11 | <1 | 14 h 10 min |
| September | 74°F | 39°F | 56.5°F | 1.26 | 0.4 | 6 | 3 | 3 | 12 h 40 min |
| October | 59°F | 29°F | 43.7°F | 1.57 | 4.8 | 7 | <1 | 17 | 11 h |
| November | 45°F | 19°F | 32.1°F | 0.70 | 6.5 | 5 | <1 | 26 | 9 h 30 min |
| December | 36°F | 11°F | 23.4°F | 0.58 | 9.1 | 5 | <1 | 29 | 8 h 40 min |
| Year (annual) | 59°F | 29°F | 43.7°F | 14.54 | 50.9 | 81 | 29 | 185 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 2°C | −12°C | −5.1°C | 13 mm | 20 cm |
| February | 4°C | −11°C | −3.7°C | 14 mm | 24 cm |
| March | 9°C | −7°C | 1.2°C | 21 mm | 20 cm |
| April | 14°C | −3°C | 5.3°C | 48 mm | 10 cm |
| May | 19°C | 2°C | 10.6°C | 68 mm | 2 cm |
| June | 24°C | 7°C | 15.6°C | 54 mm | 0 cm |
| July | 30°C | 10°C | 19.9°C | 24 mm | 0 cm |
| August | 29°C | 9°C | 18.9°C | 22 mm | 0 cm |
| September | 23°C | 4°C | 13.6°C | 32 mm | 1 cm |
| October | 15°C | −2°C | 6.5°C | 40 mm | 12 cm |
| November | 7°C | −7°C | 0.1°C | 18 mm | 17 cm |
| December | 2°C | −12°C | −4.8°C | 15 mm | 23 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00244506; 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 Joliet?
Normal highs sit between 65°F and 85°F in May, June, August and September. Of those, August 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 USC00244506.
When is the last frost in Joliet?
In Joliet, the last spring frost (32°F) comes after May 29 in half of years and after June 17 in one year in ten; the first autumn frost comes before September 15 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 291 year in 10 after June 17; 9 in 10 after May 14
- First autumn frost, half of years before
- September 151 year in 10 before September 1; 9 in 10 before October 1
NOAA puts the median frost-free season at 107 days, and the season without a hard freeze (28°F) at 134 days.
A hard freeze (28°F) comes after May 13 in half of springs and before September 26 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Joliet in zone 5a in ZIP code 59041, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Joliet's NOAA station is in zone 4b: the coldest night of a typical year reaches −21°F (27 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 USC00244506; 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 Joliet?
In a normal year in Joliet, 29 days a year reach 90°F (2 of them 100°F or more), 185 nights fall to 32°F or colder and 81 days bring measurable precipitation.
- Days at 90°F or more
- 29a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 185a normal year
- Days that stay below freezing
- 35high of 32°F or less
- Days with 0.01 inch of precipitation
- 81a normal year
- Days with 1 inch of snow or more
- 18a normal year
The highest temperature in this station's record (since 1956) is 106°F, on July 15, 2002; the lowest is −39°F, on December 24, 1983.
The wettest calendar year on that record is 2018, with 21.89 in; the snowiest season is 2013–14, with 102.4 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00244506; records: ACIS (NOAA Regional Climate Centers), station USC00244506. Records use complete months only; a month missing more than three days is left out.
How sunny is Joliet?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Joliet, 4.1 kWh per square metre a day. July is the sunniest month (85%) and April the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 75% | 1.9 |
| February | 76% | 2.8 |
| March | 70% | 3.8 |
| April | 66% | 4.7 |
| May | 69% | 5.7 |
| June | 77% | 6.7 |
| July | 85% | 7.1 |
| August | 84% | 6.0 |
| September | 80% | 4.6 |
| October | 72% | 2.9 |
| November | 70% | 1.9 |
| December | 67% | 1.4 |
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 Joliet need?
A normal year in Joliet brings 7,999 heating degree days, 49% more than the median U.S. place (5,373), and 266 cooling degree days, 71% 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 1,788 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,307 | 0 |
| February | 1,112 | 0 |
| March | 960 | 0 |
| April | 704 | 0 |
| May | 436 | 2 |
| June | 174 | 26 |
| July | 38 | 124 |
| August | 63 | 97 |
| September | 271 | 16 |
| October | 661 | 0 |
| November | 987 | 0 |
| December | 1,288 | 0 |
| Year (annual) | 7,999 | 266 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00244506. 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 Joliet been warmer than normal lately?
Over 48 complete years from 1957 to 2020, the station's annual mean temperature rose at a fitted 3.4°F per century (+0.19°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Joliet's climate compare?
Joliet is warmer than 64 of the other 140 places with their own NOAA record in Montana, and wetter than 58. Across the 7,247 U.S. stations with normals, its annual mean of 43.7°F is warmer than 14%.
In the Köppen classification computed from these normals, Joliet is Dfb: continental, no dry season, 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.
Which places near Joliet share this climate record?
6 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.
- Park City, MT934 people · 12 mi N
- Rockvale, MT413 people · 7 mi NE
- Montaqua, MT108 people · 5 mi NE
- Edgar, MT79 people · 7 mi E
- Boyd, MT26 people · 3 mi SW
- Silesia, MT10 people · 10 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 Joliet's climate
What is the coldest month in Joliet?
January, with a normal high of 36°F and a normal low of 10°F. The warmest is July (86°F by day, 50°F at night).
Does it snow in Joliet?
Yes: 51 inches in a normal year, falling on 26 days with 0.1 inch or more, the most in February (9.5 inches).
What is the rainiest month in Joliet?
May, with 2.67 in of precipitation in a normal year; the driest is January with 0.53 in.
What plant hardiness zone is Joliet in?
The USDA's 2023 map puts Joliet in zone 5a in ZIP code 59041, the nearest ZIP area. By the same method at Joliet's NOAA station, the coldest night of a typical year reaches −21°F (27 years, 1991-2020): zone 4b.
How late can frost come in Joliet?
In half of years the last 32°F night comes after May 29; in one year in ten it comes after June 17. Waiting until June 17 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Bridger, MT11 miles from this station, 45.7°F a year
- Columbus, MT17 miles from this station, 44.4°F a year
- Red Lodge, MT24 miles from this station, 43.4°F a year
- Billings, MT32 miles from this station, 48.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made