St. Mary's, CO climate
St. Mary's has cold, snowy winters and cool summers. A typical July afternoon reaches 71°, a January night drops to 14°, and about 214 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in St. Mary's feels like
Winter
Spring
Summer
Fall
St. Mary's 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 | 31° | 14° | 1.4" | 33.2" | 13 | 31 | 18° – 29° |
| February | 33° | 14° | 1.7" | 30.8" | 11 | 29 | 19° – 30° |
| March | 40° | 19° | 2.3" | 31.9" | 11 | 30 | 25° – 35° |
| April | 46° | 23° | 3.2" | 31.5" | 11 | 25 | 29° – 40° |
| May | 55° | 32° | 2.6" | 11.2" | 10 | 8 | 38° – 48° |
| June | 66° | 40° | 1.6" | 1.0" | 7 | 0 | 49° – 58° |
| July | 71° | 46° | 2.4" | 0 | 10 | 0 | 55° – 63° |
| August | 69° | 45° | 2.2" | 0 | 12 | 0 | 53° – 61° |
| September | 62° | 38° | 1.8" | 1.3" | 9 | 1 | 45° – 54° |
| October | 50° | 29° | 1.6" | 14.2" | 8 | 8 | 33° – 44° |
| November | 39° | 20° | 1.4" | 26.8" | 11 | 24 | 21° – 37° |
| December | 31° | 14° | 1.4" | 32.1" | 12 | 31 | 17° – 27° |
| Year | 49° | 28° | 23.6" | 214.0" | 124 | 186 |
“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 St. Mary's
St. Mary's gets 24 inches of rain and melted snow a year. April is the wettest month and December the driest. Rain or snow falls on about 124 days a year. Snow covers the ground about 186 days of the year.
About 103 frost-free days a year
In half of years the last 32° night comes by June 6 and the first one by September 19. That leaves about 103 frost-free days for gardens, shorter than 99% of U.S. towns.
Heating and cooling a home in St. Mary's
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In St. Mary's, 100% of that work is heating and 0% 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 St. Mary's 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 St. Mary's averaged 1.3° warmer than the 1900s. The biggest change is in March (+2.9°). The shift is larger than in 58% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at St. Mary's’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. November swings the most: between 1991 and 2020 its average temperature ranged from 21° to 37°. July is the most reliable, staying within 8°.
Common questions about St. Mary's’s climate
What is the coldest month in St. Mary's?
December, with a typical high of 31° and a low of 14°.
What is the hottest month in St. Mary's?
July, with a typical high of 71° and a low of 46°.
How much snow does St. Mary's get?
About 214 inches in a normal winter, most of it in January.
When is the first frost in St. Mary's?
In half of years the first 32° night comes by September 19, and the last spring frost by June 6.
What is the rainiest month in St. Mary's?
April, with 3.2 inches of rain and melted snow. The year totals 24 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for St. Mary's itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Winter Park, CO (8 mi, snow) and Cabin Creek, CO (12 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.