Swan Lake, Montana climate: Normal weather by month, frost dates and records
Swan Lake's normal year runs from 18°F January nights to 82°F July afternoons. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.4°C, January lows of −8°C, July highs of 28°C.
- NOAA stationSwan Lake
- Station IDUSC00248087
- Location47.92°N 113.84°W
- Elevation3,100 ft (945 m)
- Population (census place)226
On October 23, the normal high in Swan Lake is 51°F and the normal low 30°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Swan Lake.
- Jan 31° 18°
- Feb 36° 18°
- Mar 45° 26°
- Apr 54° 31°
- May 64° 38°
- Jun 71° 44°
- Jul 82° 48°
- Aug 82° 46°
- Sep 70° 39°
- Oct 55° 32°
- Nov 39° 26°
- Dec 30° 20°
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 Swan Lake each month?
July is the warmest month, with normal highs of 82°F; January the coldest, with normal lows of 18°F.
| Month | High | Low | Mean | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|
| January | 31°F | 18°F | 24.3°F | – | <1 | 30 | 8 h 50 min |
| February | 36°F | 18°F | 27.0°F | – | <1 | 28 | 10 h 10 min |
| March | 45°F | 26°F | 35.4°F | – | <1 | 29 | 11 h 50 min |
| April | 54°F | 31°F | 42.7°F | – | <1 | 22 | 13 h 40 min |
| May | 64°F | 38°F | 51.2°F | – | <1 | 9 | 15 h 10 min |
| June | 71°F | 44°F | 57.6°F | – | 1 | 1 | 16 h |
| July | 82°F | 48°F | 64.7°F | – | 6 | <1 | 15 h 40 min |
| August | 82°F | 46°F | 63.8°F | – | 7 | 1 | 14 h 20 min |
| September | 70°F | 39°F | 54.5°F | – | 1 | 6 | 12 h 40 min |
| October | 55°F | 32°F | 43.4°F | – | <1 | 20 | 11 h |
| November | 39°F | 26°F | 32.2°F | – | <1 | 27 | 9 h 20 min |
| December | 30°F | 20°F | 25.3°F | – | <1 | 30 | 8 h 30 min |
| Year (annual) | 55°F | 32°F | 43.5°F | – | 16 | 204 |
The same normals in °C and millimetres
| Month | High | Low | Mean |
|---|---|---|---|
| January | −1°C | −8°C | −4.3°C |
| February | 2°C | −8°C | −2.8°C |
| March | 7°C | −4°C | 1.9°C |
| April | 12°C | 0°C | 5.9°C |
| May | 18°C | 3°C | 10.7°C |
| June | 22°C | 7°C | 14.2°C |
| July | 28°C | 9°C | 18.2°C |
| August | 28°C | 8°C | 17.7°C |
| September | 21°C | 4°C | 12.5°C |
| October | 13°C | 0°C | 6.3°C |
| November | 4°C | −4°C | 0.1°C |
| December | −1°C | −7°C | −3.7°C |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Creston (23 miles away), gets 51 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00248087; 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 Swan Lake?
Normal highs sit between 65°F and 85°F in June, July, August and September.
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 USC00248087.
When is the last frost in Swan Lake?
In Swan Lake, the last spring frost (32°F) comes after May 17 in half of years and after June 4 in one year in ten; the first autumn frost comes before September 19 in half of years and before September 4 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 171 year in 10 after June 4; 9 in 10 after May 4
- First autumn frost, half of years before
- September 191 year in 10 before September 4; 9 in 10 before October 2
NOAA puts the median frost-free season at 121 days, and the season without a hard freeze (28°F) at 153 days.
A hard freeze (28°F) comes after April 30 in half of springs and before October 1 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Swan Lake in zone 5b in ZIP code 59911, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Swan Lake's NOAA station is in zone 5b: the coldest night of a typical year reaches −14°F (18 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 USC00248087; 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 Swan Lake?
In a normal year in Swan Lake, 16 days a year reach 90°F and 204 nights fall to 32°F or colder.
- Days at 90°F or more
- 16a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 204a normal year
- Days that stay below freezing
- 47high of 32°F or less
The highest temperature in this station's record (since 1963) is 106°F, on August 11, 2018; the lowest is −40°F, on December 30, 1968.
The wettest calendar year on that record is 1964, with 37.73 in; the snowiest season is 1996–97, with 256.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00248087; records: ACIS (NOAA Regional Climate Centers), station USC00248087. Records use complete months only; a month missing more than three days is left out.
How sunny is Swan Lake?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Swan Lake, 3.9 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (60%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 64% | 1.4 |
| February | 69% | 2.4 |
| March | 66% | 3.5 |
| April | 66% | 4.6 |
| May | 67% | 5.6 |
| June | 73% | 6.4 |
| July | 87% | 7.3 |
| August | 83% | 5.9 |
| September | 77% | 4.3 |
| October | 69% | 2.6 |
| November | 61% | 1.5 |
| December | 60% | 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 Swan Lake need?
A normal year in Swan Lake brings 7,953 heating degree days, 48% more than the median U.S. place (5,373), and 142 cooling degree days, 84% fewer than the median (908). Nine months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 1,429 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,263 | 0 |
| February | 1,064 | 0 |
| March | 918 | 0 |
| April | 669 | 0 |
| May | 431 | 1 |
| June | 235 | 11 |
| July | 78 | 68 |
| August | 94 | 59 |
| September | 318 | 3 |
| October | 668 | 0 |
| November | 984 | 0 |
| December | 1,232 | 0 |
| Year (annual) | 7,953 | 142 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00248087. 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 Swan Lake been warmer than normal lately?
2023 averaged 46.0°F, 2.5°F above the 1991-2020 normal of 43.5°F. 3 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal |
|---|---|---|
| 2021 | 45.8°F | +2.3°F |
| 2022 | 44.4°F | +0.9°F |
| 2023 | 46.0°F | +2.5°F |
Source: observed years: ACIS, station USC00248087. A year counts only with all twelve months complete.
How does Swan Lake's climate compare?
Swan Lake is warmer than 56 of the other 140 places with their own NOAA record in Montana. Across the 7,247 U.S. stations with normals, its annual mean of 43.5°F is warmer than 14%.
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers.
Questions about Swan Lake's climate
What is the coldest month in Swan Lake?
January, with a normal high of 31°F and a normal low of 18°F. The warmest is July (82°F by day, 48°F at night).
Does it snow in Swan Lake?
Yes. NOAA publishes no 1991-2020 snowfall normal for Swan Lake's NOAA station; the nearest record that keeps one, Creston (23 miles away), records 51 inches of snow in a normal year.
What plant hardiness zone is Swan Lake in?
The USDA's 2023 map puts Swan Lake in zone 5b in ZIP code 59911, the nearest ZIP area. By the same method at Swan Lake's NOAA station, the coldest night of a typical year reaches −14°F (18 years, 1991-2020): zone 5b.
How late can frost come in Swan Lake?
In half of years the last 32°F night comes after May 17; in one year in ten it comes after June 4. Waiting until June 4 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Bigfork (13 mi S), MT9 miles from this station, 46.8°F a year
- Creston, MT23 miles from this station, 44.4°F a year
- Polson, MT24 miles from this station, 46.2°F a year
- SKQ Dam, MT25 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