Donald Gansauer of Canton tracks snow on radar maps: "I noticed the colors on the map stand for reflectivity measured in dBZ. Is reflectivity the amount of the signal being reflected back to the radar antenna? What is a dBZ?" It's complicated, but yes, reflectivity measures how well drops, flakes or ice reflect the signal, which depends on their number, size and shape. The dBZ (for decibels) scale measures relative signal intensity. Warmer colors, higher numbers indicate more wet or frozen stuff in the sky.