Eureka, Montana climate: Normal weather by month, frost dates and records
Eureka's normal year runs from 19°F January nights to 87°F July afternoons, with 15.0 inches of precipitation and 35 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.3°C, January lows of −7°C, July highs of 30°C, 381 mm of precipitation a year.
- NOAA stationEureka Ranger Station
- Station IDUSC00242827
- Location48.90°N 115.06°W
- Elevation2,532 ft (772 m)
- Population1,561
On October 14, the normal high in Eureka is 59°F and the normal low 36°F, and the chance of measurable rain or snow is 27%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Eureka.
- Jan 32° 19°
- Feb 39° 21°
- Mar 49° 28°
- Apr 60° 34°
- May 70° 42°
- Jun 77° 49°
- Jul 87° 53°
- Aug 86° 51°
- Sep 75° 44°
- Oct 57° 35°
- Nov 41° 27°
- Dec 31° 21°
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 Eureka each month?
July is the warmest month, with normal highs of 87°F; January the coldest, with normal lows of 19°F. The most precipitation falls in June (2.53 in), the least in February (0.72 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 32°F | 19°F | 25.8°F | 0.92 | 8.5 | 11 | <1 | 27 | 8 h 40 min |
| February | 39°F | 21°F | 29.8°F | 0.72 | 5.9 | 8 | <1 | 24 | 10 h 10 min |
| March | 49°F | 28°F | 38.3°F | 0.90 | 3.7 | 9 | <1 | 22 | 11 h 50 min |
| April | 60°F | 34°F | 46.8°F | 1.00 | 1.0 | 9 | <1 | 14 | 13 h 40 min |
| May | 70°F | 42°F | 55.9°F | 1.78 | 0.2 | 10 | <1 | 4 | 15 h 10 min |
| June | 77°F | 49°F | 62.5°F | 2.53 | 0.0 | 10 | 2 | <1 | 16 h 10 min |
| July | 87°F | 53°F | 69.6°F | 1.13 | 0.0 | 7 | 11 | <1 | 15 h 50 min |
| August | 86°F | 51°F | 68.6°F | 1.05 | 0.0 | 5 | 11 | <1 | 14 h 30 min |
| September | 75°F | 44°F | 59.4°F | 1.27 | 0.0 | 7 | 1 | 2 | 12 h 40 min |
| October | 57°F | 35°F | 46.3°F | 1.24 | 0.6 | 9 | <1 | 13 | 10 h 50 min |
| November | 41°F | 27°F | 34.4°F | 1.24 | 5.0 | 9 | <1 | 20 | 9 h 10 min |
| December | 31°F | 21°F | 26.1°F | 1.22 | 10.2 | 10 | <1 | 27 | 8 h 20 min |
| Year (annual) | 59°F | 35°F | 47.0°F | 15.00 | 35.1 | 103 | 26 | 153 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 0°C | −7°C | −3.4°C | 23 mm | 22 cm |
| February | 4°C | −6°C | −1.2°C | 18 mm | 15 cm |
| March | 10°C | −2°C | 3.5°C | 23 mm | 9 cm |
| April | 15°C | 1°C | 8.2°C | 25 mm | 3 cm |
| May | 21°C | 5°C | 13.3°C | 45 mm | 1 cm |
| June | 25°C | 9°C | 16.9°C | 64 mm | 0 cm |
| July | 30°C | 12°C | 20.9°C | 29 mm | 0 cm |
| August | 30°C | 11°C | 20.3°C | 27 mm | 0 cm |
| September | 24°C | 7°C | 15.2°C | 32 mm | 0 cm |
| October | 14°C | 2°C | 7.9°C | 31 mm | 2 cm |
| November | 5°C | −3°C | 1.3°C | 31 mm | 13 cm |
| December | 0°C | −6°C | −3.3°C | 31 mm | 26 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00242827; 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 Eureka?
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 USC00242827.
When is the last frost in Eureka?
In Eureka, the last spring frost (32°F) comes after May 11 in half of years and after May 25 in one year in ten; the first autumn frost comes before September 27 in half of years and before September 10 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 111 year in 10 after May 25; 9 in 10 after April 28
- First autumn frost, half of years before
- September 271 year in 10 before September 10; 9 in 10 before October 9
NOAA puts the median frost-free season at 138 days, and the season without a hard freeze (28°F) at 164 days.
A hard freeze (28°F) comes after April 28 in half of springs and before October 7 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Eureka in zone 5b in ZIP code 59930, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Eureka's NOAA station is in zone 5a: the coldest night of a typical year reaches −15°F (29 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 USC00242827; 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 Eureka?
In a normal year in Eureka, 26 days a year reach 90°F (2 of them 100°F or more), 153 nights fall to 32°F or colder and 103 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
- 153a normal year
- Days that stay below freezing
- 42high of 32°F or less
- Days with 0.01 inch of precipitation
- 103a normal year
- Days with 1 inch of snow or more
- 13a normal year
The highest temperature in this station's record (since 1960) is 106°F, on June 30, 2021; the lowest is −35°F, on January 11, 1963.
The wettest calendar year on that record is 1996, with 22.26 in; the snowiest season is 1996–97, with 101.6 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00242827; records: ACIS (NOAA Regional Climate Centers), station USC00242827. Records use complete months only; a month missing more than three days is left out.
How sunny is Eureka?
Over a year 70% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Eureka, 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 Eureka need?
A normal year in Eureka brings 6,948 heating degree days, 29% more than the median U.S. place (5,373), and 400 cooling degree days, 56% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,158 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,215 | 0 |
| February | 984 | 0 |
| March | 826 | 0 |
| April | 546 | 0 |
| May | 293 | 10 |
| June | 119 | 46 |
| July | 27 | 169 |
| August | 37 | 148 |
| September | 196 | 26 |
| October | 582 | 0 |
| November | 918 | 0 |
| December | 1,206 | 0 |
| Year (annual) | 6,948 | 400 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00242827. 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 Eureka been warmer than normal lately?
2024 averaged 49.1°F, 2.1°F above the 1991-2020 normal of 47.0°F. 3 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 49.0°F | +2.0°F | 11.73 | 8.4 |
| 2023 | 49.2°F | +2.2°F | 10.41 | 5.7 |
| 2024 | 49.1°F | +2.1°F | 10.58 | – |
Over 50 complete years from 1961 to 2024, the station's annual mean temperature rose at a fitted 6.0°F per century (+0.33°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00242827; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Eureka's climate compare?
Eureka is warmer than 128 of the other 140 places with their own NOAA record in Montana, and wetter than 71. Across the 7,247 U.S. stations with normals, its annual mean of 47.0°F is warmer than 28%.
In the Köppen classification computed from these normals, Eureka 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 Eureka share this climate record?
3 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.
- West Kootenai, MT397 people · 8 mi NW
- Rexford, MT87 people · 5 mi W
- Indian Springs, MT0 people · 4 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 Eureka's climate
What is the coldest month in Eureka?
January, with a normal high of 32°F and a normal low of 19°F. The warmest is July (87°F by day, 53°F at night).
Does it snow in Eureka?
Yes: 35 inches in a normal year, falling on 22 days with 0.1 inch or more, the most in December (10.2 inches).
What is the rainiest month in Eureka?
June, with 2.53 in of precipitation in a normal year; the driest is February with 0.72 in.
What plant hardiness zone is Eureka in?
The USDA's 2023 map puts Eureka in zone 5b in ZIP code 59930, the nearest ZIP area. By the same method at Eureka's NOAA station, the coldest night of a typical year reaches −15°F (29 years, 1991-2020): zone 5a.
How late can frost come in Eureka?
In half of years the last 32°F night comes after May 11; in one year in ten it comes after May 25. Waiting until May 25 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Montana climateThe statewide normals and every place in the state
- Fortine, MT11 miles from this station, 43.9°F a year
- Yaak, MT26 miles from this station, 41.0°F a year
- Olney, MT33 miles from this station, 39.6°F a year
- Libby Dam (Base), MT35 miles from this station, 46.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made