Weather & Climate in Dewey, MT

Temperature, precipitation, air quality, natural hazards, and monthly weather data.

Dewey has a cool climate with an average annual temperature of 41°F (5°C). Winters average 22°F in January while summers reach 64°F in July. The area gets 311 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 11.3 inches (drier than the 38-inch national average). The area receives 15.2 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 5,502 feet.

Temperature

22°F Jan (-6°C) 64°F Jul (18°C)

Annual Average	41.0°F
	24% below US avg
January Average	22°F (-6°C)
July Average	64°F (18°C)
Sunny Days	311 days/yr

Geography

Elevation	5,502 ft (1,677 m)
Area	0.3 sq mi (0.7 km²)
Population Density	104/sq mi
Coordinates	45.7754°N, 112.8529°W
Timezone	America/Denver
County	Silver Bow County County
Nearest Airport	Helena Regional (HLN) 71 miles away

Precipitation & Snow

Annual Rainfall 11.3"

70% below US avg

Snowfall 15.2"

Wettest Month (Jun) 2.20"

Driest Month (Feb) 0.47"

Air Quality

AQI Median	26.0
Rating	Good

Natural Hazard Risk

Overall Risk	Very Low
Risk Score	38.0 / 100
Social Vulnerability	17.0 / 100
Community Resilience	62.9 / 100

Hazard Breakdown

Tornado	Very Low
Earthquake	Relatively Low
Wildfire	Relatively Low
Flood	Very Low
Hail	Very Low
Strong Wind	Very Low
Heat Wave	Very Low
Winter Weather	Relatively High
Lightning	Relatively Moderate
Ice Storm	Very Low
Drought	Very Low
Cold Wave	Relatively Moderate
Landslide	Relatively Moderate
Avalanche	Very Low

Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

644 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M5.8.

Jul 6, 2017	11 km SE of Lincoln, Montana	M5.8	125 km	12 km
Jul 26, 2005	16 km N of Dillon, Montana	M5.6	49 km	13 km
Aug 20, 1999	22 km NW of Lima, Montana	M5.1	110 km	16 km
Jul 6, 2017	15 km S of Lincoln, Montana	M5.0	116 km	15 km
Apr 9, 2019	9 km NE of Lima, Montana	M4.6	123 km	14 km
Feb 5, 2006	44 km NE of Spencer, Idaho	M4.4	143 km	14 km
May 8, 2007	8 km NNW of Alder, Montana	M4.4	71 km	14 km
Jul 6, 2017	14 km SE of Lincoln, Montana	M4.4	123 km	10 km
Apr 5, 2011	28 km NNE of Spencer, Idaho	M4.4	143 km	12 km
Jun 13, 2016	45 km W of Hebgen Lake Estates, Montana	M4.3	144 km	10 km
Jan 30, 2016	19 km E of Lincoln, Montana	M4.3	134 km	2 km
Oct 28, 1998	18 km S of Whitehall, Montana	M4.3	57 km	5 km
Jul 14, 2023	3 km S of Lima, Montana	M4.2	131 km	12 km
Aug 16, 2019	4 km NW of Manhattan, Montana	M4.2	116 km	2 km
Aug 30, 1997	25 km WNW of Hebgen Lake Estates, Montana	M4.1	149 km	4 km
Jun 18, 2006	6 km S of Pony, Montana	M4.1	76 km	12 km
Oct 7, 2024	11 km E of Dillon, Montana	M4.1	67 km	17 km
Aug 6, 2019	3 km NW of Manhattan, Montana	M4.1	117 km	5 km
Apr 8, 2000	8 km ENE of Townsend, Montana	M4.1	128 km	5 km
Sep 3, 2016	16 km S of Whitehall, Montana	M4.0	57 km	8 km

Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

17 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2.

Date	Rating	Distance	Path	Fatalities
Jun 14, 1962	EF2	60 km	0.1 mi	0
May 19, 1962	EF2	54 km	2.0 mi	0
Jul 3, 1988	EF1	63 km	0.2 mi	0
Jun 28, 1982	EF1	71 km	0.5 mi	0
Jun 6, 1976	EF1	61 km	3.0 mi	0
May 29, 1965	EF1	20 km	0.1 mi	0
Aug 20, 2018	EF0	48 km	0.8 mi	0
Jul 10, 2016	EF0	64 km	0.0 mi	0
Sep 15, 1997	EF0	36 km	0.1 mi	0
Jul 19, 1997	EF0	62 km	0.1 mi	0
Jun 29, 1992	EF0	90 km	0.1 mi	0
May 16, 1991	EF0	47 km	0.2 mi	0
Aug 11, 1988	EF0	77 km	2.0 mi	0
May 4, 1971	EF0	98 km	0.5 mi	0
Jul 14, 1962	EF0	60 km	0.1 mi	0
May 17, 1962	EF0	72 km	0.1 mi	0
Aug 2, 1959	EF0	46 km	0.1 mi	0

Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).

Wildfire History

20 wildfires (100+ acres) recorded within 100 km. Largest: VALLEY COMPLEX (BEAR) (118,045 acres, 2000).

Year	Name	Acres Burned	Distance
2000	VALLEY COMPLEX (BEAR)	118,045	99 km
2017	MEYERS	68,711	59 km
2000	MUSSIGBROD COMPLEX (MUSSIGBROD)	64,810	60 km
2000	SULA COMPLEX (MAYNARD)	62,967	86 km
2021	TRAIL CREEK	62,432	73 km
2021	ALDER CREEK	38,189	23 km
2017	LITTLE HOGBACK	34,646	92 km
2007	ROMBO MOUNTAIN	28,215	100 km
2021	HAYSTACK	26,118	64 km
2007	RAT CREEK	25,929	70 km
2000	VALLEY COMPLEX (COYOTE)	20,601	85 km
2022	TRAIL RIDGE	19,532	75 km
2006	CLARKS CANYON	14,848	81 km
2007	PATTENGAIL CREEK	13,471	28 km
2011	FORTY ONE COMPLEX	12,679	93 km
2005	SIGNAL ROCK	12,653	81 km
2000	MIDDLE FORK COMPLEX (COUGAR CREEK)	11,655	76 km
2018	GOLDSTONE	9,812	91 km
2000	BOULDER COMPLEX (HIGH ORE ROAD)	9,625	80 km
1988	COMBINATION	8,588	84 km

Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month	Avg Temperature	Precipitation	Summary
January	22°F (-6°C)	0.7 in
February	22°F (-6°C)	0.5 in	Driest
March	26°F (-3°C)	0.8 in
April	33°F (1°C)	1.1 in
May	41°F (5°C)	2.0 in
June	49°F (10°C)	2.2 in	Wettest
July	64°F (18°C)	1.3 in	Warmest
August	55°F (13°C)	1.5 in
September	47°F (8°C)	1.4 in
October	38°F (3°C)	0.8 in
November	27°F (-3°C)	0.8 in
December	19°F (-7°C)	0.8 in	Coldest

Dewey has a seasonal temperature swing of 45°F / from 19°F in December to 64°F in July. Total annual precipitation is 13.8 inches, with June being the wettest month (2.2") and February the driest (0.5").

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