Boulder Snow by Month: Averages, Records and Upslope Storms

calendar Oct 23, 2026 / · 8 min read · boulder weather snow snowfall records snowstorms upslope winter weather front range colorado weather  ·
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Boulder's Snow Season at a Glance

Late October is when Boulder's snow season starts to count: the average first measurable snow at the official station falls on October 17. Under the 1991-2020 climatology at the NIST site, Boulder averages 89.71 inches of snow a year, February is the snowiest month at 14.78 inches, and June through August average zero. The monthly snowfall record runs from 1889 to September 2026. Two big March storms, in 2003 and 2024, show how fast totals climb between town and the foothills.

How Much Snow Falls in Each Month?

Since 1990, Boulder's official readings have come from a station near the NIST building on the western edge of town, south of the main campus. From 1947 to 1989 the Boulder Fire Department made the observations. That puts all of the 1991-2020 averages at the NIST site.

The 1991-2020 means in season order, September to May:

MonthMean snowfall (in)Mean snow per day (in)
September1.030.0343
October6.950.224
November12.690.423
December12.330.398
January11.760.374
February14.780.523
March14.590.471
April13.590.453
May1.990.064

Six months do most of the work. November through April each average more than 11 inches. September and May together average about 3.

March and April each average more snow than December or January. March's 14.59 inches is less than two-tenths behind February, and April's 13.59 beats both December (12.33) and January (11.76).

The per-day column is each month's total divided by its number of days. That is why February leads it at 0.523 inches a day by a wider margin than its total alone suggests: it has the highest average and the fewest days.

Totals come two ways: by snow year, September to June, labeled with the June year, and by calendar year. The row marked 2020 holds both the 2019-20 season and calendar 2020.

How Much Does a Boulder Winter Swing From the Average?

The standard deviation for each month measures how far a typical year lands from the mean. April's is the largest at 12.59 inches, almost as big as its 13.59-inch average. February follows at 12.23. January's 7.74 is the smallest of the six snowiest months, which makes it the steadiest of them.

In October, September and May the standard deviation is larger than the average itself: 9.17 against 6.95 in October, 2.34 against 1.03 in September, 3.24 against 1.99 in May. October 1969 brought 49.3 inches, while October 2024 and October 2025 each recorded 0.0.

Whole seasons swing as far. The 2019-20 snow year brought 152.0 inches, the most of any season in the table, with 39.1 inches in February 2020 and 37.3 in April 2020. January 2020 in that same season recorded 0.0. The 1981-82 snow year brought 20.8 inches, the least in the table. The snowiest season had more than seven times the snow of the leanest.

By calendar year, 1997 holds the top spot at 158.7 inches, with 38.6 inches in April and 30.1 in October.

The season that ended this past spring was a lean one. The 2025-26 snow year totaled 41.4 inches, less than half the 89.71-inch annual average. January 2026 had 10.7 inches, March 5.4 and April 1.7. February 2026, the month with the highest average, recorded 0.0. May 2026 then brought 11.3 inches, more than five times its 1.99-inch mean.

When Does the First and Last Snow Fall?

The first-snow and last-snow dates count measurable snow, meaning more than a trace, at the official Boulder station (currently NIST).

The first measurable snow, tracked since 1948, arrives on October 17 on average. The earliest first snow came on September 8, 2020, and the latest on November 29, 2025.

The last measurable snow, from 1949-2014 statistics, comes on April 27 on average. The earliest last snow was March 22, 1992, and the latest was June 7, 1993. A trace of snow fell on June 5, 1953, still the snow record for that date.

From the average first snow to the average last snow is about six months, mid-October to late April.

The edge months have produced large single totals. September 1971 brought 21.0 inches, the most of any September in the table, against a September average of 1.03. May 1931 brought 26.7 inches, the record for May.

What Are Boulder's Biggest Snow Months and Storms?

These records span every station the city has used. Observations were made at sites in the western part of the city to 1912, near or on the campus from 1912 to 1947, by the Fire Department from 1947 to 1989, and near NIST from 1990, with no official station for one year between 1989 and 1990. Only the 1991-2020 averages above come from a single site, so a record month from 1913 and one from 2015 were measured in different places.

The snowiest month on record for each part of the season:

MonthRecord (in)Year
September21.01971
October49.31969
November46.71946
December52.51913
January35.01948
February54.62015
March56.71970
April47.62013
May26.71931

March 1970's 56.7 inches is the largest single month in the table. One day accounts for about a third of it: March 30, 1970 produced 18.5 inches, still the daily record for that date.

April 2013's 47.6 inches was followed by 12.3 inches in May 2013, more than six times the May average.

December 1913's 52.5 inches came in the same month as Denver's all-time record single storm, 37.5 inches on December 4-5, 1913. That 37.5-inch figure is Denver's, not Boulder's.

Daily snow records start in 1948, and hail counts toward them, so a daily record does not always mean snow alone. Those years cover the Fire Department and NIST sites. Only four daily records reach 20 inches:

Below those comes March 30, 1970 at 18.5 inches, then a tie at 18.0 inches between September 17, 1971 and December 24, 1982. The September 1971 day accounts for most of that month's record 21.0 inches.

None of the four 20-inch days falls in December, January or February. Two fell in November, one in October and one in April. The October 1997 day is part of the 158.7-inch 1997 calendar year. The November 2019 day fell in the 152.0-inch 2019-20 season, which had already logged 26.4 inches in October 2019.

The March 2003 and March 2024 Storms Around Boulder

The March 17-20, 2003 storm left 22.5 inches in Boulder at the NOAA Building. Totals rose sharply west of town:

Boulder 7SW had more than twice the NOAA Building's 22.5 inches, and Allenspark had about three times as much. Longmont got 16.0 inches, less than the NOAA Building. Foothills towns west of the city have their own pages, including Sugarloaf and Gold Hill.

Up to 135,000 people lost power during the storm. For the whole month, the official Boulder station recorded 34.7 inches in March 2003. In Denver, it was the most snow from a single storm since the 1913 record.

The March 13-15, 2024 storm was the most significant snowfall for the foothills of Boulder through Jefferson Counties since March 2003. Across the Denver metro area and Boulder, accumulations mostly ranged from 10 to 18 inches, with nearly two feet from the southwestern sections of Boulder into the Golden area. In the Boulder County foothills, 4 ENE Nederland measured 53.0 inches. The official total at DIA was 5.7 inches.

Snow fell at 1 to 2 inches per hour, with rates up to 3 inches per hour in the foothills. The official station recorded 29.6 inches for March 2024.

Why Did the March 2024 Storm Drop So Much Snow?

Upslope flow is air that flows toward higher terrain and is forced to rise. When the air is stable, that extra lift often brings widespread low cloud and steady, stratiform precipitation.

The March 2024 storm did not take the usual track for heavy snow in northeast Colorado. Heavy March snow normally comes from storms that develop in the Four Corners region, track east across the New Mexico/Colorado border area, and then move into the Texas/Oklahoma Panhandles or western Kansas. In 2024 a deep low dropped almost straight south from Idaho to near Las Vegas, Nevada, and then into the Mojave Desert, a track that does not favor heavy snow.

Moisture and lift made up for the track. Precipitable water values climbed to near the maximum observed for that time of year, and the snow came with persistent and deep upslope flow in and near the Front Range Foothills. Snow tapered off late Thursday night into the early hours of Friday, March 15, as the upslope flow weakened.

References

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