It's just a theory but some scientists believe that lightning strikes are provoked by traffic. Honk if you like thunder!
A study by researchers from the Hebrew University of Jerusalem found that in south west US states, lightning strikes near major roadways increased up to 25% during weekdays, coinciding with pollution increases. Look for next next next gen Prius's to have lightning rods on their rooftops. [New Scientist via BLDGBLOG , image from Garry''s]