![]() ![]() Naturally, it is influenced by the amount of precipitation that falls as snow. "Snow cover" refers to the amount of land covered by snow at any given time. In contrast, the first date of snow cover in the fall has remained relatively unchanged. By far the largest change has taken place in the spring, with the last day of snow shifting earlier by 19 days since 1972. snow cover season became shorter by nearly two weeks, on average (see Figure 3). Spring and summer snow cover can have a particularly important influence on water supplies. Decreases in snow cover have largely occurred in spring and summer, whereas winter snow cover has remained fairly steady over the time period studied and fall snow cover has increased (see Figure 2).The annual average area covered by snow during the most recent decade (2011–2020) was 3.25 million square miles, which is about 2 percent smaller than the annual average extent during the first 10 years of measurement (1972–1981)-a difference of 77,700 square miles, or an area approximately the size of Nebraska (see Figure 1). ![]() Between 19, the average extent of North American snow cover decreased at a rate of about 1,870 square miles per year.The average area covered by snow has ranged from 3.0 million to 3.6 million square miles, with the minimum value occurring in 1998 and the maximum in 1978 (see Figure 1). The extent of snow cover has varied from year to year.When averaged over the entire year, snow covered an average of 3.25 million square miles of North America during the period from 1972 to 2020 (see Figure 1). ![]()
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