Use the 30-30 rule to determine the threat of lightning in your area. Clear the field if conditions are unsafe. Under no circumstances should you try to ‘get the game in’ unless the 30-30 guidelines are followed.
30 seconds: Count the seconds between seeing lightning and hearing thunder. If this time is less than 30 seconds, lightning is still a potential threat. Seek shelter immediately.
30 minutes: After the last lightning flash, wait 30 minutes before leaving shelter. Half of all lightning deaths occur after a storm passes. Stay in a safe area until you are sure the threat has passed.
Lightning is an electrical discharge caused when static electricity builds up between thunderclouds, or thunderclouds and the ground. Lightning strokes carry up to 100 million volts of electricity and leap from cloud to cloud, or cloud to ground and vice versa. Lightning tends to strike higher ground and prominent objects, especially good conductors of electricity such as metal.
Thunder is the noise caused by the explosive expansion of air due to the heat generated by a lightning discharge. Thunder may have a sharp cracking sound when lightning is close by, compared to a rumbling noise produced by more distant strokes. Because light travels at a faster speed than sound, you can see a lightning bolt before the sound of thunder reaches you.
To judge how close lightning is, count the seconds between the flash and the thunder clap. Each second represents about 300 meters. If you can count less than 30 seconds between the lightning strike and the thunder, the storm is less than 10 km away and there is an 80 percent chance the next strike will happen within that 10 km. If you count less than 30 seconds, take shelter, preferably in a house or all-metal automobile (not a convertible top) or in a low-lying area.
Lightning may strike several kilometers away from the parent cloud and precautions should be taken even if the thunderstorm is not directly overhead. If caught outdoors:
- If caught in a level field far from shelter and you feel your hair stand on end, lightning may be about to hit you. Kneel on the ground immediately, with feet together, place your hands on your knees and bend forward. Don’t lie flat.
- If you are in a group in the open , spread out, keeping people several yards apart.
- Keep a safe distance from tall objects, such as trees, hilltops, and telephone poles.
- Avoid projecting above the surrounding landscape.
- Seek shelter in low-lying areas such as valleys, ditches and depressions but be aware of flooding.
- Stay away from water. Don’t go boating or swimming if a storm threatens and land as quickly as possible if you are on the water. Lightning can strike the water and travel some distance from its point of contact. Don’t stand in puddles even if you are wearing rubber boots.
- Stay away from objects that conduct electricity, such as tractors, golf carts, golf clubs, metal fences, motorcycles, lawnmowers and bicycles.
- Avoid being the highest point in an open area. Swinging a golf club or holding an umbrella or fishing rod can make you the tallest object and a target for lightning. Take off shoes with metal cleats.
- You are safe inside a car during lightning, but don’t park near or under trees or other tall objects which may topple over during a storm. Be aware of downed power lines which may be touching your car. You are safe inside the car, but you may receive a shock if you step outside.
- In a forest, seek shelter in a low-lying area under a thick growth of small trees or bushes.
- Keep alert for flash floods, sometimes caused by heavy rainfall, if seeking shelter in a ditch or low-lying area.
Note: Persons who have been struck by lightning receive an electrical shock but do not carry an electrical charge and can be safely handled. Victims may be suffering from burns or shock and should receive medical attention immediately. If breathing has stopped, mouth-to-mouth resuscitation should be administered. If breathing and pulse are absent, cardio-pulmonary resuscitation is required.