If the temperature is 30 degrees F, why do we sometimes get snow and other times 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, 32 degrees Fahrenheit (0 degrees Celsius) outside. That is useful information, but if it is 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. The local weather report only gives us the ground-level temperature. In order to understand sleet, snow and freezing rain, what we would need 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 32 F (0 C). 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 we get sleet. Or, if the layer of sub-freezing air at ground level is thin, the precipitation falls as rain but then freezes
