Sweet Grass, MT climate
Sweet Grass has cold winters and pleasant summers, with very little rain. A typical July afternoon reaches 80°, a January night drops to 10°.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Sweet Grass feels like
Winter
Spring
Summer
Fall
Sweet Grass weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 32° | 10° | 0.4" | 6° – 35° |
| February | 34° | 11° | 0.4" | -3° – 36° |
| March | 43° | 19° | 0.6" | 13° – 40° |
| April | 53° | 29° | 1.3" | 35° – 46° |
| May | 64° | 38° | 2.1" | 46° – 57° |
| June | 71° | 45° | 3.8" | 55° – 63° |
| July | 80° | 50° | 1.3" | 56° – 73° |
| August | 80° | 49° | 1.3" | 58° – 69° |
| September | 69° | 41° | 1.3" | 51° – 62° |
| October | 55° | 30° | 0.9" | 36° – 49° |
| November | 41° | 19° | 0.6" | 17° – 40° |
| December | 33° | 11° | 0.3" | 9° – 33° |
| Year | 55° | 29° | 14.2" |
“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 Sweet Grass
Sweet Grass gets 14 inches of rain and melted snow a year. June is the wettest month and December the driest.
About 132 frost-free days a year
In half of years the last 32° night comes by May 15 and the first one by September 25. That leaves about 132 frost-free days for gardens, shorter than 94% of U.S. towns.
Heating and cooling a home in Sweet Grass
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Sweet Grass, 96% of that work is heating and 4% 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 Sweet Grass 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 Sweet Grass averaged 1.8° warmer than the 1900s. The biggest change is in January (+5.6°). The shift is larger than in 85% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Sweet Grass’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 -3° to 36°. June is the most reliable, staying within 8°.
Common questions about Sweet Grass’s climate
What is the coldest month in Sweet Grass?
January, with a typical high of 32° and a low of 10°.
What is the hottest month in Sweet Grass?
July, with a typical high of 80° and a low of 50°. About 16 days a year reach 90°.
When is the first frost in Sweet Grass?
In half of years the first 32° night comes by September 25, and the last spring frost by May 15.
What is the rainiest month in Sweet Grass?
June, with 3.8 inches of rain and melted snow. The year totals 14 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Sweet Grass itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Sweetgrass, MT (1 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.