What happens if there's thunder or lightning at an outdoor pool?

The NFHS guidelines for handling contests during lightning (detailed in the NFHS Sports Medicine Handbook) are the default policy:

• When thunder is heard or a cloud-to-ground lightning bolt is seen, the storm is close enough to strike. Suspend competition and take shelter immediately.
• 30-minute rule: wait at least 30 minutes after the last thunder or lightning before resuming.
• Any thunder or lightning during the 30 minutes resets the clock, and a new 30-minute count starts.

The guidelines also call for staff to monitor the weather, and for an evacuation plan with nearby shelters identified in advance. State associations and schools may adopt their own policies.