Welcome to Brainstuff from house stuff works dot com where smart happens. Hi Am Marshall Brain with today's question, if the temperature is thirty degrees fahrenheit outside, why do we sometimes get snow and other times we get freezing rain. When you watch the local weather report on the evening news, you always hear the current temperature. It may be, for example, thirty two degrees fahrenheit or zero degrees celsius outside. That's useful information, but if it's precipitating, it is only one
part of the puzzle. It turns out that the atmosphere is layered, and these layers control the form that precipitation will take on the ground. The local weather report only gives us the ground level temperature. In order to understand sleet, snow, and freezing rain. What we need to know is perhaps four to six different temperature readings at different altitudes. Precipitation starts in the cloud as snow. As it falls, it may travel through a layer of air that has a
temperature greater than thirty two degrees fahrenheit. This layer melts the snow into rain. If the temperature at ground level is below freezing, then the water may refreeze in the air and then we get sleep. Or if the layer of subfreezing air at ground level is thin, the precipitation falls as rain, but then it freezes once it touches the freezing object on the ground. For snow to fall, all the layers of air that the snow falls through
once it leaves the cloud must be sub freezing. The warm middle layers are normally caused by the movement of warm fronts or cold fronts through the area. In the southeast, temperatures often hover around thirty two degrees Fahrenheits, so the form of precipitation can change all the time. In more northern areas, the temperature is well below freezing in all
the layers, so snow is a sure thing. You have any ideas or suggestions for this podcast, If so, please send me an email at podcast at how stuff works dot com. For more on this and thousands of other topics, go to how stuff works dot com and be sure to check out the brain stuff blog on the how stuff works dot com home page.