This M.Y. question cites Shulchan Aruch O.C. 227 that states that as long as it is overcast, one recites the blessing on lightning / thunder once (unless the storm continues into the next day.) If it clears up, then storms again, one makes a new bracha.
What if one is in a place and there is a storm. He makes the bracha. It clears in his area. Then he drives and hits the same storm. Is this considered a new event for him so he should make a new bracha?
When the Shulchan Aruch was written, there were no cars. So, I interpreted when it said that it clears up then storms again, this is part of a new thunderstorm cell, which is why you would make a new bracha. However, if you drove back into the storm you were in, this is not a new storm. So, perhaps, you should not say a new bracha.