SSC policy regarding inclement weather (lightning):

At the first sign of lightning or thunder all persons are to leave the fields and congregate at the SSC Clubhouse. By the time the flash-to-bang count approaches 30 seconds (or is less than 30 seconds), all individuals should already be under the Clubhouse or should immediately seek a safe structure or location. 

To use the flash-to-bang method, the observer begins counting when a lightning flash is sighted.  Counting is stopped when the associated bang (thunder) is heard.  Divide this count by 5 to determine the distance to the lightning flash (in miles).  For example, a flash-to-bang count of 30 seconds equates to a distance of 6 miles.

Once activities have been suspended, all persons are to wait at least 30 minutes after the last sound of thunder or lightning flash before resuming an activity. 
 
Source: National Athletic Trainers’ Association Position Statement: Lightning Safety for Athletics and Recreation,  Journal of Athletic Training 2000