http://www.uil.utexas.edu/athletics/...ng_safety.html
Texas UIL policy for all outdoor sports is the thirty second rule on flash to bang. Most local leagues I know off use a similar rule and no lightning seen for 30 minutes minimum before restarting.
Lightning is something I would never mess with. There was a situation in Grapeland, TX in 2004 where an entire football team, 40+ people, was hit by one strike, one player killed. Everything I've ever read about the case indicated there was no previous lightning seen by anyone, no warning.