Before It Strikes
Before It Strikes
If you can hear thunder, you are close enough to be struck. Lightning regularly reaches 10 miles from the storm and can reach 20 miles under clear sky. Shelter when lightning is within 8 miles, and stay sheltered until the lightning has moved beyond 8 miles and is moving away, or for 30 minutes after the last thunder if you have no detection data.
The National Weather Service recommends three trigger distances around any outdoor venue, and the CISA guide for sports and special events builds its whole action plan on them. The action gets stronger as lightning gets closer.
| Distance | Level | What to do |
|---|---|---|
| 15 miles | Monitor | Notify officials. Position staff to direct people. If the storm is moving toward you, begin moving people now. Organized storms (squall lines, supercells) call for at least 30 minutes of lead time. |
| 12 miles | Prepare | Announce the coming delay. Staff in place. Evacuation to shelter is under way if the storm is headed for the venue. |
| 8 miles | Shelter | Suspend the activity, sound the signal, and send everyone to a lightning-safe building or a fully enclosed metal vehicle. Nobody stays outside. |
Why 8 miles is the minimum shelter distance: most lightning happens within 8 miles of a storm, but about 20 percent of strikes land beyond that, and a bolt from the blue can travel farther still. Eight miles is the floor, not a comfortable margin.
Before It Strikes uses these same three rings. Free users see them at the default distances. Pro users can set their own distances for each place they save, and organizations can set them per venue.
There are two ways to call an all-clear, and the guidance is clear about which is better.
Resume only when all three are true: lightning has moved beyond 8 miles, the storm is carrying the lightning away from you, and there is no sign of new lightning developing within 8 miles. This is the method the guide recommends, and it is the one Before It Strikes uses when it has live data, which is why its countdown can end early when a storm has clearly left.
Wait 30 minutes after the last thunder or lightning before going back out. Every new flash restarts the clock. The guide calls this a last resort, because people mishear thunder, lose count, and go out too soon. It is still far better than guessing.
Most lightning stays in the cloud. Cloud-to-ground strikes are the direct hazard. But the presence of any lightning means every kind is possible at any moment, so the official position is simple: all lightning counts. A storm with only in-cloud flashes is a storm that can produce a ground strike on its next flash.
Safe: a fully enclosed building with wiring and plumbing, or a fully enclosed metal-roofed vehicle with the windows up. Vehicles are safe because the current passes around the metal shell, not because of the tires.
Not safe: open fields, ridgelines, and being the tallest thing around; metal bleachers; pavilions, dugouts, gazebos, picnic shelters and tents; open-cab vehicles such as golf carts and convertibles; and standing under a tree. No outdoor location is completely safe.
Before It Strikes automates every step of that plan on a phone: it watches lightning nationwide in real time, pushes a warning when a storm crosses each ring around the places you save, runs the countdown, and tells you when it is safe again. See how much warning it gives against real storms.
Lightning regularly strikes 10 miles from the storm and has been documented 20 miles away under clear sky. If you can hear thunder you are within range. The recommended shelter distance is 8 miles.
Without lightning detection data, wait 30 minutes after the last thunder or flash, restarting the clock on every new flash. With real-time detection, you can go out once lightning is beyond 8 miles, moving away, and not redeveloping nearby.
They are the NOAA trigger distances used in lightning safety plans: monitor and notify at 15 miles, prepare and begin moving people at 12 miles, and suspend the event and shelter everyone at 8 miles.
Yes, in a fully enclosed metal-roofed vehicle with the windows up. The current passes around the metal shell. Convertibles, golf carts and open-cab vehicles are not safe.
No. Heat lightning is ordinary lightning from a storm too far away for the thunder to be heard. The storm can still be moving toward you.
Guidance on this page follows the National Weather Service lightning safety toolkit and the Lightning Safety Guide for Sports and Special Events published by CISA and the National Center for Spectator Sports Safety and Security (May 2026). Official NWS warnings always take precedence.
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