Some useful information from the University of Delaware regarding the benefits of a snowy winter…
The phrase “blanket of snow” is more than a visual description — it’s also accurate in terms of warmth. Freshly fallen, un-compacted snow is typically 90 to 95 percent trapped air. Because the air can barely move, heat transfer is greatly reduced, thus slowing the flow of heat from the warm ground to the cold air above.
This blanket effect makes snow an excellent insulator for gardens and landscapes, protecting these natural areas and their animal inhabitants against frigid temperatures and damaging winds.
Snow also lessens — to some extent — the extremes of temperature fluctuation to which the soil is subjected. This can be critical for some plants, including evergreens. Even in mid-winter, if air temperature within the canopy of these plants rises during the day, the plants will try to take moisture from the soil. If the soil is frozen, the plants can actually die of thirst.
The extent to which snow insulates depends on its depth. Generally, temperatures underneath a layer of snow increase about 2 degrees Fahrenheit for each inch of accumulation. Because the soil also gives off some heat, the temperature at the soil surface can be much warmer than the air temperature. Hansen says that a study done at minus 14 degrees Fahrenheit found that the soil below a 9-inch deep snow registered a surface temperature of 28 degrees.
Melting snow provides needed moisture to many plants. Even dormant plants continue to lose moisture as water evaporates through their branches. Evergreens, which keep their foliage throughout the winter, are at even greater risk of injury from lack of moisture.