Okay --- now your dragging it out of me and making me show my age
Long before smartphones with live radar App's........ the tried & true method of determining if the ominous clouds you saw off in the distance is an approaching "electrical" storm (as opposed to a simple rain storm) in the vicinity was to simply switch your onboard radio/stereo onto a low frequency AM setting (800-860) and simply listen! If lightning were occurring, you would literally "hear" it as static in the white noise of the radio band. Louder the static -- the closer the actual thunderhead!
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