Well, I feel better about worrying about it now...as some of you worry also.
Our horses are brought in whevever storms threaten. Either by us (we can be there in 15 minutes) or by the property owner (who doesn't work) who brings them in for us when storms pop up, even in the middle of the night. And she is there to monitor them 24/7.
Their barn is more like a fancy garage with 6 stalls than a barn, it has hot/cold running water and a heated bathroom and tackroom.... Their stalls are rubber matted, and the bathroom/wiring ensures that any lightning strike to or near the building would be grounded. In case of fire from a strike, her or her daughter are always there to monitor them. Someone is always home.
Their pastures, 23 acres, are either open field or surrounded by trees....not a good place to be in a storm.