A new technique for detecting and ranging lightning flashes up to approximately 100 km away is described. The technique uses a novel method of discriminating between lightning and non-lightning sources of quasi-electrostatic field change by comparison of the signal strength measured simultaneously on two co-located antennas, which is a function of their different geometry and exposure to the atmospheric electric field. In addition to detection of all types of lightning within range, the system also has the capability of detecting and classifying other sources of rapid electric field change associated with thunderstorm or shower cloud activity, such as from nearby corona brush discharge, strong space charge variability and charged precipitation. Real-time lightning flash detection and ranging combined with monitoring of initial storm electrification processes provides a comprehensive method of local severe weather warning. Since the operating frequency of 1–50 Hz lies below man-made sources of radio signals, the technique is considered especially useful for sites with strong radio interference.