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Weather & Climate in Rocky Boy's Agency, MT
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Rocky Boy's Agency has a cool climate with an average annual temperature of 44°F (6°C). Winters average 18°F in January while summers reach 70°F in July. The area gets 274 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 13.1 inches (drier than the 38-inch national average). The area receives 34.6 inches of snow annually, a moderate snowfall amount. Air quality is rated Good with a median AQI of 26 / among the cleanest air in the country. The city sits at an elevation of 3,829 feet.
Temperature
18°F Jan (-8°C)
70°F Jul (21°C)
| Annual Average | 43.5°F |
| 19% below US avg | |
| January Average | 18°F (-8°C) |
| July Average | 70°F (21°C) |
| Sunny Days | 274 days/yr |
Geography
| Elevation | 3,829 ft (1,167 m) |
| Area | 8.6 sq mi (22.2 km²) |
| Population Density | 14/sq mi |
| Coordinates | 48.2610°N, 109.7746°W |
| Timezone | America/Denver |
| County | Hill County County |
| Nearest Airport | Great Falls International (GTF) 91 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 26.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 50.5 / 100 |
| Social Vulnerability | 67.1 / 100 |
| Community Resilience | 38.1 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Earthquake | Very Low |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Very Low |
| Strong Wind | Very Low |
| Heat Wave | Very Low |
| Winter Weather | Relatively High |
| Lightning | Relatively Moderate |
| Ice Storm | Very Low |
| Drought | Relatively Low |
| Cold Wave | Relatively High |
| Landslide | Very Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
6 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.9.
| Aug 16, 1994 | 27 km W of Chester, Montana | M3.9 | 118 km | 5 km |
| Dec 5, 1991 | 15 km WSW of Hays, Montana | M3.0 | 74 km | 10 km |
| Oct 16, 2011 | Eastern Montana | M2.7 | 140 km | 21 km |
| Jul 10, 2021 | 24 km SSE of Malta, Montana | M2.7 | 148 km | 10 km |
| Feb 25, 2013 | 28 km WSW of Chester, Montana | M2.5 | 114 km | 18 km |
| Jul 15, 2015 | 48 km E of Zortman, Montana | M2.5 | 148 km | 23 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
29 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 7 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 5, 1988 | EF3 | 36 km | 12.0 mi | 0 |
| Jul 5, 1988 | EF3 | 60 km | 3.0 mi | 0 |
| Jul 5, 1988 | EF3 | 45 km | 10.0 mi | 0 |
| Jun 25, 1996 | EF2 | 96 km | 2.0 mi | 0 |
| Jul 8, 2002 | EF1 | 54 km | 2.0 mi | 0 |
| Jun 19, 1998 | EF1 | 94 km | 1.0 mi | 0 |
| Jun 16, 1995 | EF1 | 88 km | 0.1 mi | 0 |
| May 25, 1980 | EF1 | 56 km | 0.1 mi | 0 |
| May 25, 1980 | EF1 | 96 km | 0.1 mi | 0 |
| May 24, 1977 | EF1 | 81 km | 0.1 mi | 0 |
| Jul 10, 1965 | EF1 | 92 km | 0.2 mi | 0 |
| Jul 1, 1962 | EF1 | 27 km | 3.8 mi | 0 |
| Aug 26, 2022 | EF0 | 61 km | 3.1 mi | 0 |
| Jun 13, 2014 | EF0 | 44 km | 0.3 mi | 0 |
| Jun 5, 2012 | EF0 | 25 km | 1.1 mi | 0 |
| Jun 17, 2005 | EF0 | 67 km | 0.1 mi | 0 |
| Aug 5, 2002 | EF0 | 85 km | 4.0 mi | 0 |
| Jul 20, 1999 | EF0 | 98 km | 0.1 mi | 0 |
| Jul 7, 1999 | EF0 | 88 km | 0.2 mi | 0 |
| Jun 18, 1999 | EF0 | 54 km | 0.5 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Wildfire History
20 wildfires (100+ acres) recorded within 100 km. Largest: BLAINE C (138,192 acres, 1991).
| Year | Name | Acres Burned | Distance |
| 1991 | BLAINE C | 138,192 | 45 km |
| 2012 | WELDER | 32,985 | 89 km |
| 2021 | TAYLOR | 21,704 | 86 km |
| 2017 | EAST FORK | 21,165 | 15 km |
| 2021 | PINE GROVE | 16,158 | 92 km |
| 2009 | MEISSNER | 12,318 | 98 km |
| 1984 | CENTENNIAL | 11,775 | 3 km |
| 2017 | JULY | 11,409 | 98 km |
| 2006 | MAGGIE | 8,187 | 67 km |
| 2022 | EAGLE CREEK | 6,359 | 17 km |
| 1988 | MONUMENT | 5,514 | 95 km |
| 1988 | LOSTCANYON | 4,532 | 7 km |
| 2008 | CHOUTEAU CO COMPLEX | 4,365 | 60 km |
| 2003 | LAKE17 | 4,054 | 72 km |
| 2006 | HOWARD | 3,884 | 87 km |
| 2014 | MIDDLE BLACK | 3,854 | 81 km |
| 2012 | OUTHOUSE | 3,179 | 40 km |
| 1990 | ADAMS | 3,072 | 88 km |
| 1990 | QUISNO | 3,018 | 82 km |
| 2007 | CHOUTEAU CO ASST | 2,646 | 77 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 18°F (-8°C) | 0.8 in | Coldest |
| February | 22°F (-6°C) | 0.6 in | Driest |
| March | 29°F (-2°C) | 0.9 in | |
| April | 40°F (4°C) | 1.3 in | |
| May | 49°F (10°C) | 3.1 in | Wettest |
| June | 58°F (14°C) | 2.9 in | |
| July | 70°F (21°C) | 1.8 in | Warmest |
| August | 64°F (18°C) | 1.9 in | |
| September | 54°F (12°C) | 1.8 in | |
| October | 43°F (6°C) | 0.9 in | |
| November | 29°F (-2°C) | 0.6 in | |
| December | 20°F (-6°C) | 0.8 in |
Rocky Boy's Agency has a seasonal temperature swing of 52°F / from 18°F in January to 70°F in July. Total annual precipitation is 17.3 inches, with May being the wettest month (3.1") and February the driest (0.6").