The Gentu Lightning is an atmospheric phenomenon in Al' Khem. It occurs only over the mouth of the Gentu River where it empties into Lake Haali. The frequent, powerful flashes of lightning over this relatively small area are considered to be Taijitus largest single generator of tropospheric ozone.
It originates from a mass of storm clouds at a height of more than 5 km, and occurs during 140 to 160 nights a year, 10 hours per day and up to 280 times per hour. It occurs over and around Lake Haali, typically over the bog area formed where the Gentu River flows into the lake.
After appearing continually for centuries, the lightning ceased from Umbrose to Ignal 1967, apparently due to drought. This raised fears that it might have been extinguished permanently. The phenomenon reappeared after several months.