We did a downwinder in the Great South Bay and a similar thing happened. The wind really picked up toward the end and it was great - some of the biggest jumps ever - but that wind was feeding a dark area over the bay. We watched it growing, and we came in when the wind started to die and before it got ugly.
As we were packing our gear the thunder and lightning started. There were still kites out in the middle of the bay! It was scary to watch, but it looked like they got picked up by their supervisors/jetskis. I hope they made it in OK.
I hope thy made it in too. It was scary on the ocean because it started going offshore. Good thing most of us saw it coming.