In the cold weather, why isn't the precipitation always snow when temperatures are in the 30s or below?
During cold weather, not only does the temperature near the ground play a role in what type of precipitation falls, but the temperature above the surface can be critical to our precipitation type.
When temperatures are below freezing from the surface upward into the atmosphere, precipitation falls as snow.
Sometimes the section of the atmosphere above the surface and below the clouds may warm above freezing. As snow falls, it enters an area of temperatures above freezing and melts the snow. This layer of cold air near the ground refreezes the rain and forms sleet.
If temperatures warm above freezing from the ground upward towards the clouds, the precipitation falls as rain. One major exception is when the ground/surface temps are still below freezing. Freezing rain occurs when liquid rain falls, hits a cold surface, and freezes upon contact.