Where March and April Are the Snowiest

As if on cue, Winter Storm Ulmer will spread snow and high winds across portions of the West and Plains, including the Denver metro area, this week. March is the snowiest month of the year in Denver, based on 30-year average snowfall data from 1981-2010.

(MAPS: The Snowiest Month of the Year)

Alaska-based climatologist Dr. Brian Brettschneider examined monthly snowfall data from 4,376 observation sites across the U.S. that receive more than 3 inches of snow a year.

For a swath of the Rockies and High Plains, the snowiest month is March, or even April.

Brettschneider said 346 reporting stations in the U.S. claim March as their snowiest month, and another 34 claim April as their snowiest month.

(MORE: Winter Storm Central)

Some cities where March is the snowiest include (average March snowfall is noted):

• Billings, Montana: 10.2 inches
• Bismarck, North Dakota: 9.1 inches
• Denver: 10.7 inches
• Great Falls, Montana: 11.9 inches
• Rapid City, South Dakota: 8.6 inches

Here are a few locations where April is the snowiest month (average April snowfall is noted):

• Breckenridge, Colorado: 26.5 inches
• Casper, Wyoming: 11.6 inches
• Mount Rushmore, South Dakota: 11.3 inches

Of course, snow isn't confined to the Rockies and High Plains after March 1.

A broad swath from New England to the Great Lakes, northern Plains, Rockies, Cascades and Sierra Nevada picks up at least 6 inches of snow each season after March 1.

Here are average snowfalls and days with measurable snow after March 1 in some locations:

The typically heaviest March or April snowstorms, injected by Gulf of Mexico moisture making farther-northward advances, hammer the northern Plains, High Plains and Rockies.

Because of the higher elevations, it's easier for wet snow to make it to the surface.

But that's not the only spring snowmaking scenario.

Wrapped-up low-pressure systems near the East Coast, and tracking into the upper Midwest and Great Lakes, occasionally are able to tap just enough cold air near the surface to produce snow, particularly in northern New England and the northern Great Lakes.

(MORE: 5 Reasons March Weather is Frustrating)

Biggest March or Later Snowstorms

Numerous major snowstorms have occurred in March, and even into early April, for areas east of the Rockies.

As categorized by the Regional Snowfall Index (RSI), ranking snowstorm impacts ranging from category 1 to category 5 based on spatial extent, amount of snowfall and population impacted, here is a look at how many category 4 or 5 snowstorms have occurred in each region in March or April since 1900:

Northeast: 6Northern Rockies and Plains: 9Ohio Valley: 2South: 4Southeast: 5Upper Midwest: 4

(MORE: Ranking the Most Extreme U.S. Winter Storms)

One of the biggest snowstorms is the Superstorm of 1993, which was rated category 5 and impacted the Northeast, Ohio Valley and Southeast from March 11-14. This storm produced record snowfall, with up to 60 inches reported, and caused $5.5 billion in damage. Every major airport on the East Coast closed for a time during the storm, and most interstates north of Atlanta were closed.

(MORE: Superstorm 1993 Recap)

The Superstorm of 1993 ranks second on the overall list, behind the Feb. 22-28, 1969, snowstorm that impacted portions of the Northeast.

The most recent category 4 or 5 March or April snowstorm occurred just last year. Winter Storm Xanto impacted the upper Midwest and Great Lakes April 12-17, 2018, and was rated a category 4.

Xanto dumped 15.8 inches of snow on Minneapolis/St. Paul, making it the heaviest April snowstorm on record there. Green Bay, Wisconsin, picked up 24.2 inches of snow from Xanto, which was not only the city's heaviest April snowstorm, but also its second-heaviest snowstorm of all-time.

Winter Storm Xanto was also the latest-in-season category 4 or 5 snowstorm for areas east of the Plains.

For areas farther west, the latest-in-season category 4 or 5 snowstorm occurred April 24-27, 1984, and buried the Black Hills of South Dakota and the mountains of Wyoming and southern Montana under more than 3 feet of snow. Blizzard conditions were also experienced in portions of the Dakotas.

So even if there are early signs of spring, you might want to wait until at least April to put away the snowblower or shovel for the season, just to be sure.