Before It Strikes
Before It Strikes
A bolt from the blue is a cloud-to-ground lightning strike that leaves the side or top of a thunderstorm, travels horizontally for miles, and comes down under clear or calm sky far from the rain. They have been documented up to 20 miles from the storm. They are the reason a storm 8 miles away is still a danger and why blue sky overhead is not an all-clear.
Positive charge builds in the high anvil cloud that spreads out downwind from a storm. A strike from that anvil can travel a long way sideways before it reaches the ground, landing well outside the rain and often outside the area where thunder can be heard. These strikes tend to be positive and unusually powerful.
Most lightning deaths happen before the storm arrives or after people think it has passed. Both windows are bolt-from-the-blue windows. The 8 mile shelter distance and the 30 minute wait exist largely because of these strikes.
Ground-based total lightning detection sees the in-cloud activity in the anvil that precedes an anvil strike. Before It Strikes Pro watches for a storm whose anvil is spreading toward a saved place, and for strikes landing in clear-sky areas near it, and raises the status before the ground strike arrives.
A cloud-to-ground strike that travels sideways out of a thunderstorm and hits under clear sky, documented up to 20 miles from the storm.
Yes. A bolt from the blue lands under clear sky miles from the storm that produced it. Clear sky overhead is not an all-clear if a storm is within 10 to 20 miles.
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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