Some prefer to invoke Thor during a thunderstorm. You need to believe in Him first and call Him.
Invocation to Thor:
"Hail, Thor, Lord of the Hammer!
Lord of the Storm, rumbling chariot
That tears across the sky,
Lord who speaks plainly
And has no time for intrigue
And subtle ploys,
Protector of the common man,
Warrior beloved by farmers,
Help us to untwist our tongues
And speak the fiery truth
Hurled blazing like a hammer-bolt
Across the open sky!"
Found from "The Pagan Book of Hours"
This is a small piece from a fuller article of Norse Mythology site about Thor
Thor ... is one of the most prominent figures in Norse mythology. He was a major god of all branches of the Germanic peoples before their conversion to Christianity, although he reached the height of his popularity among the Scandinavians of the late Viking Age.