Thunderstorms, Lightning & Hail
Every thunderstorm produces lightning, and lightning can strike miles from the rain. In the U.S. lightning kills about 20 people a year in recent years and injures many more, many of them outdoors at work or play. The rule is simple: when thunder roars, go indoors.
- Homeowners
- Families
- Outdoor Workers
The 30-30 rule
- First 30: count the seconds between a lightning flash and the thunder. If it’s 30 seconds or less, the storm is close enough to be dangerous. Go to a safe shelter.
- Second 30: stay inside until 30 minutes after the last thunder. Storms can still strike after the rain stops or the sky brightens.
- If you can hear thunder, you are close enough to be struck.
Where to shelter
- A substantial building with plumbing and wiring, such as a house, office or store.
- A hard-topped metal vehicle with the windows closed. Don’t touch metal parts inside.
- Stay inside, away from windows and doors, and wait out the storm.
- Open structures, such as picnic shelters, tents, dugouts, carports and sheds, don’t protect you.
- Convertibles, golf carts, motorcycles and tractors without cabs don’t protect you.
- Don’t shelter under a tree or next to a tall object.
Indoors during a storm
- Lightning can travel through plumbing and wiring. Stay away from sinks, showers, tubs and washing machines, and don’t wash dishes or take a bath.
- Avoid corded phones and wired electronics. Cell phones and cordless phones are safe unless they are charging.
- Unplug sensitive equipment before the storm if you have time, or use a surge protector, though it won’t stop a direct strike. See Home Electrical Safety.
- Stay off concrete floors and walls, since they can hold metal wire.
If you are caught outside
- Get to a building or vehicle as fast as you can. There is no safe place outside during a storm.
- Get off open ground, hilltops, ridges and bodies of water. Stay away from isolated trees, poles, fences, metal equipment and water.
- If you cannot reach shelter, move to a low area away from tall objects, crouch low on the balls of your feet with your feet together, and cover your ears. This reduces risk only slightly. It is not a safe position.
- Spread out in a group so one strike doesn’t injure everyone.
Work outdoors, ladders and roofs
- Plan for weather. Check the forecast and use a lightning alert, and set a shelter location and an evacuation signal. See Weather Planning.
- Get off roofs, ladders, scaffolds, towers, cranes, lifts, tall equipment and open trenches as soon as a storm approaches, giving time to climb down safely. See Roof Work and Crane Basics.
- Stop work with power lines, water and metal, and shut down equipment that you can’t leave safely.
- OSHA has no specific lightning standard, but employers must protect workers from recognized hazards under the General Duty Clause.
If someone is struck
- A person hit by lightning does not carry a charge. It is safe to touch them.
- Call 911. Move the person to a safer place if the storm continues, but only if you can do it safely.
- Check breathing and a pulse. Lightning often causes cardiac arrest, so start CPR and use an AED if needed. See CPR & AED.
- Treat burns and other injuries, and keep them warm until help arrives. See Burn First Aid.
- Everyone who was struck needs medical care, even if they seem fine.
Hail, wind and flash floods
- Hail can break windows and injure people. Go indoors, away from windows. Cover vehicles if you can, and never go out to move them during a storm.
- Straight-line winds can topple trees and signs. Stay away from trees and power lines, and know your safe room. See Tornadoes.
- Flash floods: never drive or walk through floodwater. Turn around, don’t drown. See Hurricanes & Floods and Flooded Roads.
- Watch for downed power lines. See Downed Power Lines.
Prepare ahead
- Know the difference between a watch (conditions are right for severe storms) and a warning (a storm is happening or about to). Use a weather radio or phone alerts.
- Trim dead branches near your home and secure outdoor furniture.
- Make a family plan. See Family Emergency Plan and Emergency Kit.
- Consider lightning protection for buildings in high-risk areas.
Storm checklist
- Check the forecast; set a shelter plan and a way to get alerts
- Use the 30-30 rule: shelter at 30 seconds, wait 30 minutes after the last thunder
- Stay off plumbing, corded phones and wired electronics
- Get off roofs, ladders, towers and open ground early
- Know CPR; call 911 for anyone struck
- Never drive through floodwater
Standards & references
Last updated: