Attack of the Giant Ice Balls!

Huge hailstones fell from the cloudless sky all over Spain in January 2000. Upon further study, scientists find occurences of what they call megacryometeors in Argentina, Australia, Austria, Canada, Colombia, The Netherlands, New Zealand, and the United States.
"There have been detractors. Some meteorologists and hail experts have denounced the theories posed by Martinez-Frias, stating that formation of hail without thick highly-visible clouds is an impossibility."
There's always some scientist looking to help.