Photo: Natecation · CC BY-SA 4.0Few U.S. towns get less rain and snow than Big Arm: 12 inches a year
Midwinter brings lows of about 20°. Its July afternoons stay fresher than in 68% of U.S. towns. Compared with 1901–2000, the average now sits 1.3° higher. Garden planting can start around May 15; autumn frost returns near September 28.
A year in Big Arm at a glance
Each month’s typical high and low, and what it brings.
What stands out about Big Arm’s climate
Compared with towns across the U.S., with Big Arm’s place in Montana beside it.
What a year in Big Arm feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 134 frost-free days a year
In half of years the last 32° night comes by May 15 and the first by September 28. Day counts come from NOAA’s station at Polson, MT, 9 miles from the town’s center, 380 ft lower; frost dates and degree days from Skq Dam, MT, 8 miles away.
The 2023 USDA map puts Big Arm’s center in zone 6a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −7°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 34 inches of snow a winter
Snow, measured at Skq Dam, MT, falls mostly in December. Precipitation (rain plus melted snow) adds up to 12 inches a year; June is the wettest month and March the driest. Rain or snow falls on about 128 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Big Arm
97% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through May.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Skq Dam, MT.
Living with Big Arm’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
134 frost-free days in zone 6a. The last frost comes by May 15 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Sep 28.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 13 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Big Arm from natural hazards, avalanches are the largest share (42%); heat waves, cold waves, winter storms and ice storms together are 13%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Big Arm and similar climates
TownRatings has no climate map of the towns around Big Arm yet.
Climates most like Big Arm’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Big Arm, MT | 20° | 83° | 12" | 34" |
| Deschutes River Woods, OR | 24° | 84° | 13" | 22" |
| Edgewood, NM | 19° | 85° | 15" | 29" |
| Cimarron Hills, CO | 18° | 85° | 17" | 33" |
| Cheney, WA | 24° | 84° | 17" | 45" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Big Arm averaged 1.3° warmer than the 1900s. The biggest change is in January (+3.7°).
A smaller shift than in 57% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Big Arm compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Big Arm’s place among Montana’s.
Big Arm weather by month
Highs, lows and precipitation from NOAA’s grid at Big Arm’s center; snow, wet days and snow on the ground from Skq Dam, MT. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 32° | 20° | 0.9" | 8.4" | 13 | 18° – 33° |
| February | 37° | 21° | 0.8" | 4.2" | 10 | 16° – 36° |
| March | 47° | 27° | 0.6" | 5.0" | 12 | 29° – 42° |
| April | 56° | 33° | 0.9" | 0.9" | 12 | 40° – 51° |
| May | 66° | 41° | 1.4" | 0.0" | 12 | 48° – 58° |
| June | 73° | 47° | 2.0" | 0.0" | 13 | 56° – 68° |
| July | 83° | 52° | 0.8" | 0.0" | 7 | 58° – 75° |
| August | 83° | 51° | 0.7" | 0.0" | 6 | 62° – 71° |
| September | 72° | 43° | 1.0" | 0.0" | 8 | 54° – 63° |
| October | 56° | 33° | 1.1" | 0.7" | 11 | 38° – 50° |
| November | 41° | 26° | 1.0" | 4.7" | 13 | 27° – 40° |
| December | 32° | 21° | 1.1" | 9.7" | 13 | 20° – 32° |
| Year | 56° | 35° | 12.3" | 33.6" | 128 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 16° to 36°. August is the most reliable, staying within 9°.
Where Big Arm’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Big Arm’s center.
- Snow: Skq Dam, MT.
- Frost dates, heating and cooling: Skq Dam, MT, 8 miles away.
- Freezing nights, 90° and 100° days: Polson, MT, 9 miles from the town’s center, 380 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Big Arm’s climate
What is the weather like in Big Arm?
A typical July afternoon reaches 83°, a January night drops to 20°, and about 34 inches of snow falls in a normal winter. Colder January nights than 57% of U.S. towns; cooler July afternoons than 68% of U.S. towns.
How cold does it get in Big Arm in winter?
January nights average 20°. About 147 nights a year reach 32° or below and 4 reach 0° or below. In the coldest January of the last 30 years the month averaged 18°.
How much snow does Big Arm get?
About 34 inches in a normal winter at Skq Dam, MT, most of it in December.
How hot does it get in Big Arm?
July, with a typical high of 83° and a low of 52°. About 11 days a year reach 90° (Skq Dam, MT).
When is the first and last frost in Big Arm?
In half of years the last spring frost (32°) comes by May 15 and the first fall frost by September 28, about 134 frost-free days, at Skq Dam, MT.
What growing zone is Big Arm in?
Zone 6a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −7°.
What is the best time of year to visit Big Arm?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Big Arm getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 57% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Big Arm.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.