St. Ignatius, Montana climate: Normal weather by month, frost dates and records
St. Ignatius's normal year runs from 23°F December nights to 86°F July afternoons, with 16.7 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.7°C, December lows of −5°C, July highs of 30°C, 425 mm of precipitation a year.
- NOAA stationSaint Ignatius
- Station IDUSC00247286
- Location47.31°N 114.10°W
- Elevation2,915 ft (889 m)
- Population830
On October 14, the normal high in St. Ignatius is 60°F and the normal low 35°F, and the chance of measurable rain or snow is 25%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for St. Ignatius.
- Jan 37° 23°
- Feb 40° 22°
- Mar 51° 28°
- Apr 59° 34°
- May 69° 41°
- Jun 75° 47°
- Jul 86° 52°
- Aug 86° 51°
- Sep 75° 44°
- Oct 59° 35°
- Nov 45° 28°
- Dec 37° 23°
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 St. Ignatius each month?
July is the warmest month, with normal highs of 86°F; December the coldest, with normal lows of 23°F. The most precipitation falls in June (2.63 in), the least in March (0.94 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 37°F | 23°F | 29.7°F | 0.95 | 9 | <1 | 26 | 8 h 50 min |
| February | 40°F | 22°F | 31.1°F | 1.15 | 7 | <1 | 24 | 10 h 10 min |
| March | 51°F | 28°F | 39.3°F | 0.94 | 8 | <1 | 23 | 11 h 50 min |
| April | 59°F | 34°F | 46.7°F | 1.75 | 9 | <1 | 13 | 13 h 30 min |
| May | 69°F | 41°F | 54.8°F | 2.30 | 11 | <1 | 4 | 15 h |
| June | 75°F | 47°F | 60.9°F | 2.63 | 11 | 1 | <1 | 15 h 50 min |
| July | 86°F | 52°F | 69.1°F | 0.97 | 6 | 10 | <1 | 15 h 40 min |
| August | 86°F | 51°F | 68.3°F | 1.17 | 6 | 8 | <1 | 14 h 20 min |
| September | 75°F | 44°F | 59.4°F | 1.51 | 7 | 1 | 2 | 12 h 40 min |
| October | 59°F | 35°F | 47.0°F | 1.28 | 8 | <1 | 13 | 11 h |
| November | 45°F | 28°F | 36.1°F | 1.13 | 10 | <1 | 22 | 9 h 20 min |
| December | 37°F | 23°F | 29.5°F | 0.94 | 9 | <1 | 26 | 8 h 30 min |
| Year (annual) | 60°F | 36°F | 47.7°F | 16.72 | 99 | 20 | 152 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 3°C | −5°C | −1.3°C | 24 mm |
| February | 4°C | −5°C | −0.5°C | 29 mm |
| March | 10°C | −2°C | 4.1°C | 24 mm |
| April | 15°C | 1°C | 8.2°C | 44 mm |
| May | 20°C | 5°C | 12.7°C | 58 mm |
| June | 24°C | 8°C | 16.1°C | 67 mm |
| July | 30°C | 11°C | 20.6°C | 25 mm |
| August | 30°C | 10°C | 20.2°C | 30 mm |
| September | 24°C | 7°C | 15.2°C | 38 mm |
| October | 15°C | 1°C | 8.3°C | 33 mm |
| November | 7°C | −2°C | 2.3°C | 29 mm |
| December | 3°C | −5°C | −1.4°C | 24 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Lindbergh Lake (19 miles away), gets 137 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00247286; 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 St. Ignatius?
Normal highs sit between 65°F and 85°F in May, June 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 USC00247286.
When is the last frost in St. Ignatius?
In St. Ignatius, the last spring frost (32°F) comes after May 12 in half of years and after June 1 in one year in ten; the first autumn frost comes before October 2 in half of years and before September 19 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 121 year in 10 after June 1; 9 in 10 after April 28
- First autumn frost, half of years before
- October 21 year in 10 before September 19; 9 in 10 before October 14
NOAA puts the median frost-free season at 142 days, and the season without a hard freeze (28°F) at 166 days.
A hard freeze (28°F) comes after April 30 in half of springs and before October 12 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts St. Ignatius in zone 6a in ZIP code 59863, the nearest ZIP area.
Frost dates for every NOAA station in Montana · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00247286; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 St. Ignatius?
In a normal year in St. Ignatius, 20 days a year reach 90°F (1 of them 100°F or more), 152 nights fall to 32°F or colder and 99 days bring measurable precipitation.
- Days at 90°F or more
- 20a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 152a normal year
- Days that stay below freezing
- 34high of 32°F or less
- Days with 0.01 inch of precipitation
- 99a normal year
The highest temperature in this station's record (since 1896) is 103°F, on July 12, 1953; the lowest is −36°F, on February 15, 1936.
The wettest calendar year on that record is 1980, with 24.69 in; the snowiest season is 1955–56, with 110.8 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00247286; records: ACIS (NOAA Regional Climate Centers), station USC00247286. Records use complete months only; a month missing more than three days is left out.
How sunny is St. Ignatius?
Over a year 71% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around St. Ignatius, 3.7 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (51%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 54% | 1.1 |
| February | 60% | 2.0 |
| March | 62% | 3.2 |
| April | 66% | 4.5 |
| May | 69% | 5.6 |
| June | 71% | 6.2 |
| July | 87% | 7.3 |
| August | 84% | 6.0 |
| September | 77% | 4.2 |
| October | 66% | 2.5 |
| November | 54% | 1.3 |
| December | 51% | 0.9 |
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 St. Ignatius need?
A normal year in St. Ignatius brings 6,655 heating degree days, 24% more than the median U.S. place (5,373), and 361 cooling degree days, 60% 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 2,070 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,094 | 0 |
| February | 949 | 0 |
| March | 797 | 0 |
| April | 551 | 0 |
| May | 323 | 7 |
| June | 154 | 31 |
| July | 35 | 162 |
| August | 38 | 139 |
| September | 188 | 22 |
| October | 560 | 0 |
| November | 866 | 0 |
| December | 1,100 | 0 |
| Year (annual) | 6,655 | 361 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00247286. 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.
How does St. Ignatius's climate compare?
St. Ignatius is warmer than 134 of the other 140 places with their own NOAA record in Montana, and wetter than 100. Across the 7,247 U.S. stations with normals, its annual mean of 47.7°F is warmer than 31%.
In the Köppen classification computed from these normals, St. Ignatius 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 St. Ignatius 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.
- Arlee, MT651 people · 10 mi S
- Charlo, MT344 people · 10 mi N
- Dixon, MT270 people · 12 mi W
- Ravalli, MT174 people · 4 mi SW
- Old Agency, MT114 people · 9 mi W
- Kicking Horse, MT69 people · 10 mi N
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 St. Ignatius's climate
What is the coldest month in St. Ignatius?
December, with a normal high of 37°F and a normal low of 23°F. The warmest is July (86°F by day, 52°F at night).
Does it snow in St. Ignatius?
Yes. NOAA publishes no 1991-2020 snowfall normal for St. Ignatius's NOAA station; the nearest record that keeps one, Lindbergh Lake (19 miles away), records 137 inches of snow in a normal year.
What is the rainiest month in St. Ignatius?
June, with 2.63 in of precipitation in a normal year; the driest is March with 0.94 in.
What plant hardiness zone is St. Ignatius in?
The USDA's 2023 map puts St. Ignatius in zone 6a in ZIP code 59863, the nearest ZIP area.
How late can frost come in St. Ignatius?
In half of years the last 32°F night comes after May 12; in one year in ten it comes after June 1. Waiting until June 1 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Lindbergh Lake, MT19 miles from this station, 42.0°F a year
- Polson, MT25 miles from this station, 46.2°F a year
- SKQ Dam, MT26 miles from this station, 45.2°F a year
- Missoula, MT27 miles from this station, 45.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made