When do we have to stop for lightning or thunder?

Under the NFHS Sports Medicine Advisory Committee lightning guidelines:

• As soon as thunder is heard or lightning is seen, the storm is close enough to strike. Suspend activity and move everyone to the designated safer place.
• Wait at least 30 minutes after the last thunder or lightning before resuming.
• Any new thunder or lightning restarts the 30-minute count.
• Lightning apps or detectors can help you decide to suspend if a strike is within 10 miles, but hearing thunder or seeing lightning always takes priority over an app.

Safer places: a substantial building with plumbing and wiring where people live or work, such as a school, gym or library. Each venue should have someone assigned to monitor the weather and an evacuation plan.

These apply to outdoor practices and to cheering at outdoor games. Your state association may adopt its own version.