I've never understood this, but none of the people that I thought would know could think of a reason, either. It's probably just some simple detail that I've overlooked, but I'm stumped. So... I've always been taught that "lightning is a gigantic spark of static electricity", but I've also always been taught that "moisture and/or humidity inhibit the build-up of static electricity". Which one is correct, if either? If both of them are correct, then why are there lightning storms when it's pouring rain, but not when there is a drought?