Doppler radar works by sending out a beam of energy then measuring how much of that beam is reflected back and the time needed for the beam to return.

Objects that reflect the beam back to the Doppler radar include rain, snow, sleet and even insects. Radar images are color-coded to indicate precipitation intensity. The light blue color is the lightest precipitation and the purple and white are the heaviest.

Sometimes Doppler radar images indicate virga, or precipitation that isn't reaching the ground.