The SI unit of frequency used for weather radar waves is the hertz.
One hertz means one cycle per second. Weather radar transmits electromagnetic pulses at a specified frequency and listens for energy scattered back by raindrops, snowflakes, hail, or other targets. The radar’s frequency affects its wavelength, range, attenuation, and sensitivity to different kinds of precipitation.
Radar frequencies are often expressed in larger units such as megahertz or gigahertz. One gigahertz equals one billion hertz. Common weather-radar bands include S band, C band, and X band, each offering different trade-offs between range and sensitivity to heavy precipitation.
The hertz is named after German physicist Heinrich Hertz, whose experiments demonstrated electromagnetic waves. Frequency should not be confused with wavelength: for electromagnetic radiation, higher frequency corresponds to shorter wavelength in a vacuum.