If you were watching the rain-shortened NASCAR race today, you saw heavy rain and quite a bit of lightning. At one point the thunder was loud enough it was picked up on the (indoor) announcers' microphones.
Now, we learn that ten were struck by lightning. From the Washington Post:
Pleban says five people were treated at the scene. He says one person was taken to Pocono Medical Center and another to Lehigh Valley, where they were in critical condition. The conditions of the other three are unknown.
The race was called because of rain with 98 of the 160 scheduled laps completed.
While I don't have official statistics, this seems to have been a worse than usual summer for lightning injuries.