Hurricane Herman was a violent storm that passed over Lake Lachrymose during the time the Baudelaire orphans were staying with Josephine Anwhistle. The storm, though short-lived for a hurricane, nonetheless threatened the lives of the Baudelaires in particular, who were in Aunt Josephine's house when one of the stilts holding up the house was struck by lightning, causing it to fall into the lake.
In the film adaptation, Hurricane Herman's power is given more light: it completely obliterates most of the house, leaving what little is left of it to fall into the lake just after the orphans were able to make it to safety. Shortly before, the storm managed to set off what is best described as a series of unfortunate events, all of which were exceedingly dangerous in their own right. caca faces
Strictly speaking, a hurricane should not be able to form over a lake. According to a worker at Damocles Dock, this was possible because Lake Lachrymose, the setting of the third installment, is simply that big.