Big Arm, MT climate
Big Arm has chilly, snowy winters and pleasant summers, with very little rain. A typical July afternoon reaches 83°, a January night drops to 20°, and about 34 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Big Arm feels like
Winter
Spring
Summer
Fall
Big Arm weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 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 | 12 | 48° – 58° |
| June | 73° | 47° | 2.0" | 0 | 13 | 56° – 68° |
| July | 83° | 52° | 0.8" | 0 | 7 | 58° – 75° |
| August | 83° | 51° | 0.7" | 0 | 6 | 62° – 71° |
| September | 72° | 43° | 1.0" | 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 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Big Arm
Big Arm gets 12 inches of rain and melted snow a year. June is the wettest month and March the driest. Rain or snow falls on about 128 days a year.
About 134 frost-free days a year
In half of years the last 32° night comes by May 15 and the first one by September 28. That leaves about 134 frost-free days for gardens, shorter than 93% of U.S. towns.
Heating and cooling a home in Big Arm
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Big Arm, 97% of that work is heating and 3% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
How Big Arm compares
Compared with every U.S. town and city on TownTapestry, each counted once.
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°). The shift is larger than in 53% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Big Arm’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. February swings the most: between 1991 and 2020 its average temperature ranged from 16° to 36°. August is the most reliable, staying within 9°.
Common questions about Big Arm’s climate
What is the coldest month in Big Arm?
January, with a typical high of 32° and a low of 20°.
What is the hottest month in Big Arm?
July, with a typical high of 83° and a low of 52°. About 18 days a year reach 90°.
How much snow does Big Arm get?
About 34 inches in a normal winter, most of it in December.
When is the first frost in Big Arm?
In half of years the first 32° night comes by September 28, and the last spring frost by May 15.
What is the rainiest month in Big Arm?
June, with 2.0 inches of rain and melted snow. The year totals 12 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Big Arm itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Skq Dam, MT (8 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.