Roundup, MT climate
Roundup has cold winters and warm summers, with very little rain. A typical July afternoon reaches 87°, a January night drops to 13°, and about 24 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Roundup feels like
Winter
Spring
Summer
Fall
Roundup 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 | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 36° | 13° | 0.4" | 5.2" | 4 | 11 | 14° – 36° |
| February | 40° | 15° | 0.4" | 3.9" | 4 | 6 | 4° – 39° |
| March | 50° | 23° | 0.7" | 4.4" | 5 | 3 | 22° – 45° |
| April | 59° | 31° | 1.7" | 1.4" | 8 | 1 | 38° – 49° |
| May | 68° | 40° | 2.8" | 0.1" | 10 | 0 | 49° – 58° |
| June | 78° | 49° | 2.8" | 0 | 11 | 0 | 58° – 69° |
| July | 87° | 55° | 1.6" | 0 | 7 | 0 | 61° – 78° |
| August | 87° | 52° | 1.1" | 0 | 5 | 0 | 63° – 75° |
| September | 75° | 43° | 1.2" | 0 | 5 | 0 | 55° – 65° |
| October | 60° | 32° | 1.2" | 1.0" | 7 | 0 | 38° – 51° |
| November | 47° | 22° | 0.5" | 2.8" | 4 | 2 | 24° – 42° |
| December | 37° | 14° | 0.4" | 5.6" | 5 | 8 | 15° – 35° |
| Year | 60° | 32° | 14.7" | 24.4" | 74 | 31 |
“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 Roundup
Roundup gets 15 inches of rain and melted snow a year. June is the wettest month and February the driest. Rain or snow falls on about 74 days a year. Snow covers the ground about 31 days of the year.
About 124 frost-free days a year
In half of years the last 32° night comes by May 20 and the first one by September 21. That leaves about 124 frost-free days for gardens, shorter than 96% of U.S. towns.
Heating and cooling a home in Roundup
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Roundup, 94% of that work is heating and 6% 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 Roundup 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 Roundup averaged 1.2° warmer than the 1900s. The biggest change is in January (+3.8°). The shift is smaller than in 51% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Roundup’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 4° to 39°. May is the most reliable, staying within 9°.
Common questions about Roundup’s climate
What is the coldest month in Roundup?
January, with a typical high of 36° and a low of 13°.
What is the hottest month in Roundup?
July, with a typical high of 87° and a low of 55°. About 44 days a year reach 90°.
How much snow does Roundup get?
About 24 inches in a normal winter, most of it in December.
When is the first frost in Roundup?
In half of years the first 32° night comes by September 21, and the last spring frost by May 20.
What is the rainiest month in Roundup?
June, with 2.8 inches of rain and melted snow. The year totals 15 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Roundup itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Roundup, MT (1 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.