Climate Change Delays First Frost and Reduces Autumn Snowfall Across US
Colorado’s red maple foliage contrasts vividly with early-season snow. krblokhin/iStockphoto/Getty Images
As stated by CNN
Along with the colorful leaves and changing colors, autumn in many regions of the United States brings signs of winter, but the weather itself reveals trends that differ from those of previous years. Climate changes affect when exactly the first cold morning arrives and how long the winter season lasts.
Autumn is warming due to global warming and fossil-fuel pollution, which push the date of the first frost – the moment when the temperature drops to 0°C (32°F) or below – to later dates in the year. Such a delay affects various aspects: the agricultural cycle, the allergen season, and even the duration of autumn snow cover in some areas.
According to Climate Central, since 1970 the average first frost lags by an average of 11 days in 85% of the 200 cities studied; the largest changes have been recorded in the Midwest and the Northeast.
An important factor is where you live: high-altitude regions, urban centers, proximity to the ocean or the Great Lakes, which have different influences on moderating the cold and shaping climatic conditions.
How frost dates are changing
According to NOAA for the period 1991–2020, September typically brings the first frost to high-elevation areas of the Northern and Central Rocky Mountains, as well as to areas from Dakota to the northern Great Lakes and the elevations of the Northern New England region. The frost distribution broadens in October to the Midwest, Northeast and much of the West, and in November – to the south.
The most noticeable changes have been observed in the northern belt of the United States over the last decades. The first frost lags by at least two weeks in almost fifty cities, mainly in the Upper Midwest and the Northeast, and in parts of the Northwest.
Reno, Nevada, shows one of the biggest shifts – the typical first frost is now a staggering 41 days later.
First frost can damage or destroy some plants, but not always if the cold lasts only a short time. Later frost dates sometimes lead to a longer autumn allergen season and a longer presence of mosquitoes. Warmer autumns can also affect the production of some noncitrus fruits and nuts, as the probability of a full and prolonged winter period needed for blooming and fruiting the next year decreases.
Less Snow Cover and Its Consequences
Each region of the United States is facing a decrease in autumn snowfall: the first autumn snows are becoming less frequent compared with previous decades.
If we talk about winter and spring, more than two-thirds of the more than 2,000 cities Climate Central studied receive less snow than in the 1970s. This reduction can negatively affect water resources due to less stored meltwater from snowpack, especially in the western region. It also reduces snow cover impacts on winter recreation and tourism. As global temperatures rise, winter has become one of the fastest-warming seasons in the United States – for almost 75% of the country.
The first measurable snow can be highly variable from year to year both in the autumn and winter periods. The first accumulating snow usually appears earlier in the Northern and Central Rocky Mountains, though in high-altitude regions snow can appear almost at any time of the year.
In October the first snows typically cover large parts of the Rocky Mountains, then move to the Northern Plains, the Great Lakes, and further north into the Northern New England region. In November and December, most of the Lower 48 region encounters the first accumulating snow, particularly in the Midwest, Northeast and the valleys of the Mountain West.
The country will still see snow during autumn and winter, but climate changes affect the duration and amount of snow cover. A warmer atmosphere can hold more moisture, but under conditions of fewer frosty days rain may prevail over snow.
These trends encourage people and communities to better adapt to unpredictable winter conditions and plan water management, agriculture and tourism with regard to the growing instability of the seasons.
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