Snow Depth Days
of the Northeast

This page has snow depth data for the winter of 2009-2010 at sites around New England and New York. Data for previous years are available:

A summary of several years is on the homepage.

Snow Depth Days

Traditionally, a winter's snowfall has been tracked as simply the total snow that falls during the season. While fine for several purposes, it doesn't really measure the impact of the snow on people. Suppose the total snowfall for a season is 100 inches. Near a coast where the ocean brings in warm, moist maritime air and rain, snow may not last for very long. Inland where arctic air dominates, the snow will last longer and the maximum snow depth can be much greater than near the coast.

The type of snow also has differing impacts. A foot of dry, fluffy snow will compress quickly with time (or with more snow) whereas an equal depth of wet snow presents more challenges to driving, shoveling, compression and melting.

Snow Depth Days makes a better measure of impact a winter's snows. The depth days for a whole winter are simply the sum of the snow depth on the ground for each day of the winter. Storms that start with snow and change to rain count for less than storms that are all snow.

Two major blizzards in Massachusetts show the importance of the depth day metric. If you experienced both the Blizzard of '78 and the April Fool's Blizzard of '97, the 1978 storm wins hands down despite surprisingly similar snow distributions.  The key differences were the winds (1978 saw major coastal destruction), the weight of the snow (1997 took a heavier toll on tree limbs), and how long the snow remained. Massachusetts was shut down for a week in 1978, but the 1997 snow melted in days. 1997's storm brought far fewer depth days. On, Jan 20, 1978 a storm left 22" of snow in Boston, a January record and 24 hour record. While a rain storm on Jan 26 melted most of the snow in Boston, snowbanks were still on the sides of the streets and sidewalks when the second storm hit on Feb 6th setting new 24 hour (23.6") and total storm records (27.5"). Boston and much of the rest of state simply had no place to put the new snow. Those were the bulk of the snow that year, it would be fun to go back to the climatic records and compute the depth days for each month in 1978 and 1997.

Persistence Quotient

After tracking depth days for a few years, Jim Corbin realized that dividing a season's depth days by the season's snowfall, you get another interesting metric. The quotient is a number that tells you how many days an average inch of snow lasts. If two sites have the same number of depth days but a very different persistence quotient, the one with the higher value was colder than the one with the lower quotient. It didn't snow as much, but what fell stayed longer. I think depth days is the more important metric, but it's easy and worthwhile to track persistence too. Maybe we can find a correlation between it and average temperature.

The season in review

Winter forecasts by Joe Bastardi and Joe D'Aleo called for the storm track going over the mid-Atlantic states bringing a lot of snow to areas that won't appreciate it. New England would be cold and dry. The prediction verify pretty well, except that from mid-January one the weather was warmer than expected.

Storms on that southern track often reached the Atlantic, headed north, and then steered to the left into mainland Canada. That brought them a fair amount of snow and brought us some warmer weather - from the north east!

The southern storm track did bring several snow storms to New York to Atlanta, and on Feb 12, a graduate student, Patrick T. Marsh, decided to try to collect photographs of snow from all 50 states. For a while he thought Hawaii was snow-free, but folks at the observatory poked around the north flank and found a couple patches.

Our first snow was on December 5th, kicking off snow cover from the 5th through to February 28th. December had peak snow on the ground of about 8". January started out cold, but the second half was warmer. We did get a a sub-zero low on the 30th, so the winter ws cold enough. February had generally warming temperatures throughout. One large coastal storm brought hurricane force winds to New Hampshire and took out power for some 30% of the state. The last day I recorded snow on the ground was Feb 28.

Daily/Monthly Data

The following table summarizes the snow fall and depth days from sites that are posting that data on local weather observations mail lists and a couple others. If people also prepare Web pages for daily information for their site, I'll include links to them. Cells under the "snow" column are the snowfall for the site in that month, under "SDD" are the depth days for the month.

Location October November December January February March April May
Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD Snow SDD
Fairhaven MA 21 90 4.9 51 9.3 51 2.1 2
Marlboro MA 24.1 66 17.8 109 14.2 30 0.1 0
Pepperell MA 0.4 0 20.2 179 18.1 317 20.4 216 0.1 16 0.1 0
Poland Spring ME 0.1 0 19.5 156 30.2 308 9.7 73 0.7 3
Bow NH 20.2 162 30.2 322 19.3 279 0.3 67 0.3 0
Bristol NH 19.7 160 16.4 272 17.5 109.7 0 4.5 1 0.4
Penacook NH 16.8 112 19.3 202 13.6 100 0 0 0.4 0
Charlestown RI 19.9 80 7 65 10.7 58 0.3 0
Woonsocket RI 0.1 0 22.1 87 5.8 49 9.3 17 1.5 0
Mt. Mansfield VT 8 22 4.5 49 38.3 738 42.3 1556 46.1 1916 5 2701 34 1557 0 701

2009-2010 season to end of last month

The persistence quotient is lower than the ultimate value if there is still snow on the ground at the site. This data will be updated each month.

Location Snowfall Depth Days Persistence
Fairhaven MA 37.3 194 5.2
Marlboro MA 56.2 205 3.6
Pepperell MA 59.3 728 12.3
Poland Spring ME 60.2 540 9.0
Bow NH 70.3 830 11.8
Bristol NH 54.6 546.6 10.0
Penacook NH 50.1 414 8.3
Charlestown RI 37.9 203 5.4
Woonsocket RI 38.8 153 3.9
Mt. Mansfield VT 178.2 9240 51.9


Name Location
Dennis Bollea Fairhaven MA
A Cadoret Woonsocket RI
Wayne Cotterly Poland Spring ME
Paul Hansen Marlboro MA
Jim Hilt Bow NH
Chris Seeber Charlestown RI
Paul Venditti Pepperell MA
Ric Werme Penacook NH


Jim Corbin, a meteorologist from Rhode Island, proposed the concept of both snow depth days and the persistence quotient, but he didn't have good names for them.  After a bouncing around various ideas, I came up with Depth Days.  It seems to fit into colloquial speech well, e.g. "When mired in the Depth Days of February, she thought fondly of the Dog Days of August." Of course, none of us snow lovers would ever think that. I picked Persistence Quotient while putting this page together, we'll see how it wears with time.


I think depth days is a great statistic, and I'm surprised that it is catching on slowly outside of the NE Weather Spotters mail list. I never expected that the NWS would embrace it quickly, but I had hoped that TV meteorologists would start using it, in monthly summaries, if nothing else. It would be nice if ski areas would use it, but they may not wish to if they are not likely to be #1 consistantly. (And if only one area reports depth days, it would not be a good comparative statistic.) The University of Vermont has graphs of snow depths at Stowe through many seasons.

Last update: 2015 December 31
Ric Werme

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