Earthquake Light and Earthquake Clouds
"Earthquake lights" and "earthquake clouds" are an excellent example of something that almost everyone thought was crackpot bunk, until enough photographs and first-hand experiences were accumulated by enough reputable people that it was finally acknowledged as a real thing by science. In the case of earthquake lights, it was the "earthquake swarm" that hit Nagano, Japan in 1965-1967 that did the trick.
