Updated October 2026
Fort Union National Monument Weather by Month
Fort Union National Monument is warmest in July, when the nearest NOAA climate station averages a high of 88°F and a low of 52°F, and coldest in January, with an average high of 51°F and an average low of 14°F. July is the wettest month, with about 3.1 inches of precipitation. Snowfall is heaviest in December, at about 5.4 inches.
These figures are NOAA's 1991–2020 climate normals, the 30-year average for each calendar month, from the nearest long-record weather station, 8 miles from the park's reference point. A single station cannot describe a whole park: temperatures elsewhere in Fort Union National Monument can differ from these, particularly with elevation.
Warmest month
Jul
88°F avg high
Coldest month
Jan
14°F avg low
Wettest month
Jul
3.1 in avg
Snowiest month
Dec
5.4 in avg
Longest days
Jun
14.4 h of daylight
Average weather at Fort Union by month
| Month | Avg high | Avg low | Precipitation | Snowfall | Daylight |
|---|---|---|---|---|---|
| January | 51°F | 14°F | 0.4 in | 4.2 in | 9.8 h |
| February | 54°F | 17°F | 0.6 in | 4.7 in | 10.7 h |
| March | 60°F | 22°F | 0.7 in | 3.4 in | 11.7 h |
| April | 67°F | 29°F | 0.8 in | 2.4 in | 12.9 h |
| May | 75°F | 38°F | 1.5 in | 0.1 in | 13.9 h |
| June | 85°F | 46°F | 1.7 in | 0.0 in | 14.4 h |
| July | 88°F | 52°F | 3.1 in | 0.0 in | 14.2 h |
| August | 85°F | 51°F | 2.8 in | 0.0 in | 13.4 h |
| September | 80°F | 43°F | 2.1 in | 0.0 in | 12.2 h |
| October | 71°F | 32°F | 1.2 in | 0.8 in | 11.1 h |
| November | 60°F | 21°F | 0.5 in | 2.7 in | 10.1 h |
| December | 51°F | 15°F | 0.5 in | 5.4 in | 9.6 h |
| Year total | 15.9 in | 23.7 in |
NOAA 1991–2020 climate normals from station USC00299330, 8 miles from the park's reference point. Daylight is the monthly average, computed from the park's latitude. Each month links to how crowded Fort Union is at that time of year.
Fort Union weather by season
Winter: December to February
Average highs climb from 51°F in December to 54°F in February, with average lows between 14°F and 17°F. The average low is at or below freezing in all three months. Together the three months average 1.5 inches of precipitation, about 9% of the yearly total and less than in any other season. Snowfall averages about 14 inches for the season. Daylight is at its shortest, about 9.6 hours in December.
Spring: March to May
Average highs climb from 60°F in March to 75°F in May, with average lows between 22°F and 38°F. The average low is at or below freezing in March and April. Together the three months average 3 inches of precipitation, about 19% of the yearly total. Snowfall averages about 5.9 inches for the season. Daylight lengthens from about 11.7 hours in March to 13.9 in May.
Summer: June to August
Average highs peak at 88°F in July, between 85°F in June and 85°F in August, with average lows between 46°F and 52°F. Together the three months average 7.6 inches of precipitation, about 48% of the yearly total and more than in any other season. Daylight is at its longest, about 14.4 hours in June.
Fall: September to November
Average highs fall from 80°F in September to 60°F in November, with average lows between 21°F and 43°F. The average low is at or below freezing in October and November. Together the three months average 3.8 inches of precipitation, about 24% of the yearly total. Snowfall averages about 3.5 inches for the season, most of it in November. Daylight shortens from about 12.2 hours in September to 10.1 in November.
What the National Park Service says about the weather
Fort Union is situated at 6,760 feet above sea level. Daytime temperatures between June and September may exceed 90 degrees Fahrenheit. Winter temperatures often drop below 32 degrees Fahrenheit. Temperatures may vary within 50 degrees in a 24-hour period. During the winter, it is not uncommon for the temperatures to drop below 0°F (-18°C.) During the summer, expect high temperatures, intense sunlight and extremely low humidity.
Weather description courtesy of the National Park Service — official park site.
Today's forecast for Fort Union
Averages describe a typical month, not this week. For current conditions and the seven-day outlook, the National Weather Service issues a forecast for the park's reference point at 35.91°N, 105.01°W. It covers that one spot, so other elevations in the park can differ from it, as they do from the averages above.
National Weather Service forecast for Fort Union National Monument →
Weather and crowds together
July, the warmest month, sees about 1.5× the visitors of the park's average month. June is the busiest month of the year and January the quietest. To see those crowds set against the weather for all twelve months, read the best time to visit Fort Union National Monument. For hotels, cabins and rentals close to the park, see where to stay near Fort Union.
Where to stay near Fort Union
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Top-rated places to stay near Fort Union
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Frequently Asked Questions
July is the warmest month at Fort Union National Monument, with an average high of 88°F and an average low of 52°F. That is the 1991–2020 average at the nearest long-record NOAA station, 8 miles from the park's reference point. Temperatures inside the park can differ, particularly with elevation.
January is the coldest month at Fort Union National Monument, with an average low of 14°F and an average high of 51°F, based on NOAA 1991–2020 climate normals.
July is the wettest month, with about 3.1 inches of precipitation. January is the driest, at about 0.4 inches. The station records about 15.9 inches of precipitation in an average year.
Yes. The nearest long-record NOAA station, 8 miles from the park's reference point, averages about 24 inches of snow a year. December is the snowiest month, at about 5.4 inches. The station averages at least a tenth of an inch of snow in 8 of the 12 months.
Weather at nearby parks
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84 mi away · warmest in July (74°F)
111 mi away · warmest in July (93°F)
Keep exploring
Sources: NOAA NCEI U.S. Climate Normals 1991–2020 (station USC00299330), daylight computed from latitude, weather description from the National Park Service, crowd levels from National Park Service Visitor Use Statistics (1979–2025). Updated 2026-10-11. Lodging results are provided by Stay22; WhenToVisitParks may earn a commission from bookings, at no extra cost to you.