Radar is a remote sensing tool used by weather forecasters to analyse the extent and intensity of precipitation. Radar detects objects by transmitting radio waves which are reflected back to the starting point by any object they encounter. Distance can be calculated using the speed of the radio waves and the amount of time that each pulse takes to reach the object and return back to the starting point. Rain, snow and hail all stop the radio waves. The more pulses that are reflected back, the greater the intensity of the precipitation, shown on RainToday by darkening shades of red.
NB at ranges over 90-100km, the accuracy decreases due to the natural curve of the earth and in some instances when the air is very dry near the surface some falling precipitation will have evaporated before it reaches the ground.