Above: A scene at the NOAA/NIST campus in Boulder, Colorado, on the morning of Friday, April 17, 2020. Boulder had received 17.7” of snow in the prior 24 hours, and the low that morning of 9°F was the city’s coldest on record so late in the year. (Bob Henson)
On April 16-17, Boulder, Colorado was buried by 17.7” of snow after receiving 18.7” on April 12-13. It was one of Boulder’s latest, greatest weeks of heavy spring snowfall on record. This being said, not so far away at Silver Lake, Colorado an incredible 75.8” of snow fell in 24 hours on April 14-15, 1921, which remains the U.S. national record for the greatest 24-hour snowfall ever measured. For most of the contiguous United States, April snowfall may be quite rare, but April is actually the snowiest month of the year for some isolated locations in the Rocky Mountains and the Black Hills of South Dakota.
So what are the latest dates that measurable snowfall has ever been measured in the U.S.? Below are two maps, one illustrating when, on average, the last snowfall occurs and the other showing when the latest measurable snowfall on record has occurred.
As mentioned in the caption, the first map above uses only primary U.S. weather stations with at least 15 years of records since 1980.
Below is a list of the actual latest dates of measurable snowfall for 30 select cities and the average date of the last measurable snowfall of the season for each site.
It’s interesting to note that Atlanta’s latest measurable snowfall occurred only a few days earlier than that of New York City’s (April 25 versus April 29). Also of interest is that the latest snow on record in Flagstaff, Arizona, occurred on June 8. June is normally when Arizona measures its hottest temperatures of the year; the state’s all-time record of 128°F was observed at Havasu City on June 29, 1994.
Some Historic Late-Season Snowfalls in the U.S.
Here is a list of some U.S. cities that have observed their all-time greatest 24-hour snowfalls (for any month) during April or May:
Pueblo, Colorado: 16.8”, April 29-30, 1990
Sioux City, Iowa: 20.0”, April 10,1 913
Billings, Montana: 23.7”, April 4, 1955
Butte, Montana: 30.5”, May 27-28, 1927
Scottsbluff, Nebraska: 17.6”, April 25, 1935
Ely, Nevada: 16.0”, April 7, 1900
Akron, Ohio: 20.6”, April 3-4, 1987
Abilene, Texas: 9.3”, April 5, 1996
Sheridan, Wyoming: 26.7”, April 3-4, 1955
Lander, Wyoming: 28.6”, April 24, 1999
Worcester, Massachusetts: 33.0”, March 31-April 1, 1997
Boston, Massachusetts: 25.4”, March 31-April 1, 1997
Detroit, Michigan: 24.5”, April 6, 1886
Minot, North Dakota: 27.0”, April 27-28, 1984 (state record for any month)
Some all-time 24-hour state records have also been set in April or even May aside from the national record at Silver Lake, Colorado, mentioned earlier and the North Dakota record in the above list. Montana’s state record for such was an amazing 48.0” at Shonkin on the even more amazing dates of May 28-29, 1982! Here are a few more:
Ohio: 30.0” in 24 hours near Warren on April 20, 1901.
Iowa: 24.0” at Lenox on April 20, 1918
Nevada: 45.0” at Glenbrook on April 4, 1958
Massachusetts: 36.0” at Milford on March 31-April 1, 1997
Great California Storm of April 20-23, 1880
The greatest single-storm snowfall on record in the U.S. was 194” (over 16 feet!) that fell during a massive spring blizzard at the Sierra Nevada railway summit station of Norden over the four-day period of April 20-23, 1880. Sacramento, California’s capital city, received a record two-day rainfall of 8.37” during this event.
Southern Appalachian Big Snow Events
The Southern Appalachians have also recorded some phenomenal late-season snowfalls including a reported 60.0” accumulation at Newfound Gap, North Carolina, on April 2-5, 1987, and another (even more incredible) 60.0” accumulation at Mount Pisgah, North Carolina, on May 5-8, 1992! These were not official measurements, however.
The April 27-28, 1928 Appalachian Snowstorm
The greatest late-April snow on record for the Appalachians was that of April 27-28, 1928, when up to 40” of snow fell in the mountains of West Virginia. This storm formed in the Gulf of Mexico with a secondary low centered over western North Carolina. The storms converged off the coast of Virginia and slowly moved north. Cold air aloft dropped the snow levels to about 2000’ in the central Appalachian region. Maximum state snowfalls were said to have been 40” in West Virginia (with 19” at Elkins), 36” in Pennsylvania, 15.5” in Kentucky, 14.0” in Virginia, and 13.0” in North Carolina.
April Snow Event of April 22-24, 2012 in New York and Pennsylvania
A more recent late-season snow event was that which affected portions of the Appalachians and western New York State on April 22-24, 2012. The storm, however, was not quite as widespread or severe as the 1928 event or as bad as some forecasts had predicted. In the end, temperatures remained just warm enough at lower elevations to cause most precipitation to fall as rain. Only elevations above about 1500 feet received substantial accumulations. Peak state totals include 16.0” at Arkwright, New York; 14.0” at Sylvania, Pennsylvania; 6.0” at Frostburg, Maryland; 5.0” at Crawley, West Virginia; and 23.7” at Laurel Summit, Pennsylvania (elevation 2770’). Pittsburgh received no accumulation since the temperature never managed to fall below 35°F. Buffalo, New York, picked up just an inch or so.
Some Historic Pre–Weather-Bureau Late-Season Snowstorms
The May 4 Snowstorm of 1774
A general snowfall of around 4” occurred from northern Virginia to southern New England. Both Philadelphia and New York City reported “a considerable quantity of snow”. Thomas Jefferson and George Washington both noted the event in their diaries.
The Great April Fool's Day Snow of 1807
Probably the deepest April snowfall in the history of the Ohio Valley and Mid-Atlantic occurred on April 1, 1807, from Illinois to the Northeast. The track of the storm was not the usual coastal nor’easter variety (that normally produces great snowstorms) but rather a low that moved northeast from the lower Tennessee Valley and across the mid-Atlantic states and offshore around New York City. To the north of the storm’s path, incredible snowfalls were reported. The westernmost report we have came from Vincennes on the Illinois-Indiana border with an 11” accumulation, but it was in Pennsylvania, New York, and New England that astonishing snowfall was reported, including: 52” at Montrose, Pennsylvania, near Scranton; 54” at Utica, New York; 52” at Lunenburg, Vermont; 60” at Danville, Vermont; 48” at Montpelier, Vermont; and 42-48” at Norfolk, Connecticut.
The June 1816 Snows of the “Year without a Summer”
The most famous of all cold and snowy late-season events in North America would have to be the infamous 1816 ”Year without a Summer”, with snowfall observed in June in the eastern U.S. and Canada. On June 6, accumulating snow was observed as far south as the Catskills in New York (where one inch was reported) and the highlands of central and northwest Pennsylvania. Snowflakes were seen at sea level as far south as 10 miles north of tidewater on the Hudson River, just north of New York City. The deepest accumulations were reported in the mountains of Vermont, where drifts of 12”-18” were measured. Quebec City in Canada reported 12”, with drifts up to two feet deep.
The Even-Greater Snow of June 1842
It should be noted that June snowfall in the Northeast is not an event unique to 1816. On June 11, 1842, widespread snow fell over northern New York and New England and snowflakes were observed in Cleveland, Ohio; Boston, Massachusetts; and even Harrisburg, Pennsylvania. Accumulations of 10-12” were common in Vermont, so this event may actually have been more extreme than the famous snow of June 1816.
Pennsylvania July Snowfalls
Ben Gelber mentions in his book The Pennsylvania Weather Book the strange occurrence of snow flurries in the state’s highlands of Bradford County on July 4, 1859. Snow flurries also occurred here again on July 2, 1918.
REFERENCES FOR PRE-USWB SNOWFALLS: Early American Winters: Vol 1: 1604-1820 and Vol 2: 1821-1870 by David M. Ludlum, American Meteorological Society, 1966, 1968.
KUDOS: Thanks to Brian Brettschneider (University of Alaska Fairbanks) for the maps reproduced above.
Christopher C. Burt
Weather Historian
