Variable: Snowfall | Snow Days | Snow
Yearly 4 inch or greater snowfalls (NY |
VT); Yearly 6 inch or greater snowfalls (NY | VT)
Student Contributors: Ryan Aylward, Mississippi State
University; Jordan Scampoli, St. Michaels College
Across the North Country, snowfall generally begins in October and continues
through April. The higher elevations receive more snowfall and have a longer snow season (e.g.,
Mount Mansfield's snow season typically extends into May). Maximum monthly snowfall typically
occurs in January.
At Burlington, January is typically the snowiest month with median snowfall of 19.5 inches. The
record snowiest month since records began was December 1970 with 56.7 inches.
Most sites, and months, show a downward skew of the median snowfall with respect to the middle
50% of the data (i.e., the "box" portion of the graph). A downward skewed median indicates
that more years had snowfall in the lower half of the middle 50% of the box than the upper portion.
In other words, fewer "big" snow months occur relative to lower snowfall months with
regard to the middle 50% of the data.
Gouverneur and Tupper Lake, located in Northern New York and closest to Lake Ontario, have a
greater variance of the middle 50% of snowfall in January. This is likely due to lake effect
snowfall. The lake effect can be highly variable from year to year, as snow bands can produce
excessive snowfall in one location, but very little snowfall only a few miles away. The high
variance is reduced in February as the lake freezes over and the lake effect snow 'machine'
is shut down.
Also included are yearly occurrences of 4 in. or greater, and 6 in. or greater snowfalls. These
values correspond to local snow advisory, and winter storm warning criteria, respectively, for a 12
hour period as used by your National Weather Service in Burlington. The median number of 4 inch or
greater snowfalls in a year at Burlington is 5, with the middle 50% of years between 4 and 6 events.
The median number of 6 inch or greater snowfalls in a year at Burlington is 2, with the middle 50%
of years between 1-3 such events.
How to Read Box and Whisker Graphs
Box and whisker graphs are used to visualize the data. The intent of the box and whisker format
is to give a comprehensive depiction of the variable range, skewness, and extreme values. This
provides more detailed information about the variable than, say, a simple statistical mean would. It
also facilitates comparison between different months and station locations around WFO
Burlington's forecast area.
An example of the diagram format is shown at left. The shaded region of each graph (i.e.,
"the box") shows the middle 50% of the variable range. The top of the box is the 25th
percentile and the bottom is the 75th percentile. The solid line within the box indicates the median
(or 50th percentile). The lines extending upward and downward from the box (i.e., "the
whiskers") reach to the 10th and 90th percentile of the data distribution. That is, only 10% of
the data lies above and below the ends of the whiskers. Lastly, the "x" indicates the
extreme (record) value during the entire period of record for that particular location. The period
of record is often greater than the standard 30 year period used to create the box and whisker
portion of the graph (unless otherwise noted).