Weather forecasts provide people with vital information. Sudden changes in the weather, ranging from predicted precipitation to the most violent of storms, can affect anybody at a moment’s notice.
In regard to precipitation, there are two primary types: rain and snow. Those who live in warm climates typically don’t have to worry about snow, but for people residing in colder geographic settings, snow is an inevitable fact of life, particularly during the winter season.
So why is snow always associated with cold weather? The answer is really quite simple. Regardless of location, tropical or otherwise, most precipitation begins as snow in the upper atmosphere. The higher the altitude, the lower the temperature will be. For every 1000 or so feet of elevation above sea level, the air temperature drops about 2 degrees Fahrenheit. To put this into perspective, imagine flying on an airliner. Even if it is 80 degrees at the airport, the temperature outside that cabin will have dropped to about 20 degrees Fahrenheit by the time it reaches an altitude of 30,000 feet. Thus, if that temperature on the ground was 20 degrees at takeoff, it would drop to about 40 below zero!
This is why most precipitation starts out in the form of snow. It’s cold up there! Whether it remains in this form as it reaches the ground depends on just where the freezing point of water is located. Based on the airliner example above, it is then logical to assume that if the temperature at ground level is above freezing , then the freezing point of water would have to be located at a higher altitude. In this case, the snow that forms in the upper atmosphere will pass through this barrier, warm up, and turn into rain.
In the opposite scenario, the ground temperature will be below freezing. In this instance, the air above will be even colder, so the precipitation that starts out as snow remains so when it reaches the ground. It should be noted that on occasion, a thin layer of warmer air will be located above the ground, resulting in ground temperatures slightly above freezing, but if the snow that develops above this point either falls rapidly or the warm layer itself is particularly shallow, then snow can still reach the ground intact because it didn’t have adequate time to melt and turn into rain.
Oddly enough, the optimal conditions for the heaviest accumulations of snow will occur when the ground temperature is very near the freezing point of water. The warmer the temperature, the more water vapor will exist in the form of clouds. In turn, colder temperatures result in less clouds that hold snow. In part, this is responsible for the ages-old myth that it can be “too cold to snow.”
It is never too cold to snow as many believe, because water vapor is always present in the air regardless of temperature. The amounts are smaller and will result in less accumulation, but it can still snow even if it’s more than 60 below zero Fahrenheit. Antarctica is the coldest place on the planet, and this continent still gets a few inches of snow every year.
To summarize, optimal conditions for heavy accumulations of snow that will make skiers and snowmobile enthusiasts happy occur when the temperature is just at or slightly below freezing. However, snow can still accumulate, albeit in lesser amounts, in any temperature below freezing. In certain conditions as pointed above, it can even snow when the temperature is a bit above freezing, but if the air remains warm, it won’t stay around for long.
