Lightning can be detected from thousands of miles away. See http://www.blitzortung.org/Webpages/index.php?lang=en&page_0=30 http://www.blitzortung.org/Webpages

Lightning can be detected from thousands of miles away. See http://www.blitzortung.org/Webpages/index.php?lang=en&page_0=30 http://www.blitzortung.org/Webpages/index.php?lang=en&page_0.... Turn on "detectors" on the right to see the distances involved. That site works by a using a network of cheap EMP detectors. It uses the timing differences from each sensor to trilaterate the position of the lightning strike.