Thunderstorms are a way of life in summer. In the Midwest, we’re fortunate in that we can see them building when they are several counties away, so we usually have plenty of time to organize our work around impending storms. We don’t mess around with lightning.

Lightning is the leading cause of weather-related deaths in the United States, far more than floods, tornadoes or hurricanes. On average over the last 40 years, almost 400 people a year have been hit by lightning, 20% have died and many have suffered disabling neurological problems. The greatest number of lightning strikes occur in July, followed by June and August. Two-thirds of the casualties occur between noon and 6 p.m. People involved in recreational activities account for the greatest share of lightning deaths and injuries, but farmers constitute a significant minority.

It makes sense for you to understand lightning’s dangers to protect yourself, your family and your employees. Know when it’s time to go inside, and know which buildings on your farm provide protection. Here are some facts relevant to market farmers, which I gleaned from various sources including the National Weather Service, a greenhouse manufacturer, and Extension services in Colorado, Nebraska and Maine.

Where to go
Buildings that are grounded with plumbing, electrical wires or lightning rods are the only safe places to take shelter. Open-sided sheds don’t provide protection. Ungrounded metal sheds can be outright dangerous, especially if the floor is made of concrete with wire mesh reinforcement. The entire structure would act as a lightning rod conducting the electrical charge. Since no specific ground exists on the barn for the lightning to flow through, the lighting may look for anything it can to be grounded, including a person.

Cars or trucks with the windows rolled up and enclosed tractor cabs are considered good protection as long as you’re not touching the metal frame, steering wheel, or radio. If caught in a vehicle when lightning is near, stop, roll up windows, and sit away from the door with your hands in your lap.

Greenhouses and high tunnels are not considered safe by the National Weather Service, but they are better than nothing if caught outside in a storm. A greenhouse with electrical and plumbing lines is safer, because the utilitiy lines serve as a ground for any lightning strike. We couldn't find anything specific about metal-framed hoophouses without plumbing or electric service, so we contacted the National Weather Service.

“In general, I think you would be relatively safe in your greenhouse since the grounded metal hoops along the roof ‘should’ conduct the lightning charge to the ground,” said Mike Akulow of the NWS. “The lightning heat/charge may cause a fire to the roof’s poly material. It is best also not to be touching or be near one of the metal rods, especially where they are grounded.”

We also called Stuppy’s, the manufacturer of all the greenhouses here on the Growing for Market farm, and were told by the technical support representative that a greenhouse is probably safe for several reasons. First, greenhouses are low-profile, so are less likely to be hit. Also, the metal hoops are driven into the ground, thereby creating a ground for the electricity in the lightning strike. Finally, poly is non-conductive. The rep also said that big commercial greenhouses don’t stop operations because of thunderstorms and he had never heard of anyone being injured in one by lightning.

Despite these reassurances, I would not say definitively that you are safe in a greenhouse or hoophouse. Make your own decisions about what is the safest shelter on your farm, and be sure to send your employees there well before lightning becomes a threat.

When to go
Lightning safety experts advise you to be attuned to the clouds and when you see thunderheads building, watch for distant lightning and thunder. Use the “flash to bang” method to determine the storm’s distance in miles: Count the seconds from flash of lightning to bang of thunder, then divide by five (sound travels one mile in 5 seconds). Seek shelter if the storm is within 6 miles of you, or 30 second flash to bang.

You are also advised to stay inside for 30 minutes after you no longer hear thunder. That’s because lightning often arcs out from the side of a thunderstorm; there are documented cases of lightning strikes 25 miles from the rain area of a thunderstorm, what is known as a “bolt from the blue.”
If you do get caught outside during lightning, make yourself as small as possible and with as little ground contact as possible. Squat down on the balls of your feet, tuck your head down and don’t touch the ground with your hands. Drop into this position if you ever feel the hair on your neck stand up, the usual feeling before a lightning strike, even those cases of “bolts from the blue.”
Finally, the most common cause of death in lightning strikes is cardiac arrest, so CPR can save lives. Contrary to common belief, the National Weather Service says, it is not dangerous to touch a person who has been struck by lightning.

Lynn Byczynski is the editor and publisher of Growing for Market.