It’s thunderstorm season! Actually, it’s a bit tricky to narrow thunderstorms down to one specific season since they happen year-round, but they are most common in the spring and summer months, typically during the afternoon and evening hours. Since most people have experienced a thunderstorm, regardless of where they live, there is a high level of complacency about the risks that come with wind, rain and lightning. You don’t hear about people dying in thunderstorms every day, so you’re likely not thinking about their dangers. But they are very hazardous. 

According to the Federal Emergency Management Agency (FEMA), an average of 33 people are killed and 182 people are injured each year by lightning in the U.S.—and that’s just from the storm’s electricity. Those stats don’t account for precipitation. Wet pavement affects vehicle traction and maneuverability, and rainfall reduces visibility. This is a deadly combination. Nearly 5,700 people are killed and over 544,700 people are injured in crashes on wet pavement annually, according to the U.S. Department of Transportation Federal Highway Administration, while over 3,400 people are killed and over 357,300 people are injured in crashes during rainfall every year.

Meanwhile, hail can create unseasonably icy road conditions and, according to NOAA, “tear up siding on houses, break windows and blow into houses, break side windows on cars, and cause severe injury and/or death to people and animals.” With such high levels of injury, death and destruction associated with thunderstorms, it’s crucial that we challenge our assumptions about this relatively common type of severe weather.

What is a thunderstorm?

First, we’ll start with the definition of a thunderstorm, also known as an electrical storm or a lightning storm. A thunderstorm is a violent weather disturbance that is associated with lightning, thunder, dense clouds, heavy rain or hail, and strong gusty winds. A severe thunderstorm is a thunderstorm that produces hail that is three-quarters of an inch or larger in diameter and/or winds equal to or exceeding 58 miles an hour. The National Weather Service states that every thunderstorm produces lightning, which kills more people each year than tornadoes.

There are four types of thunderstorms: single-cell, multicellular cluster, squall line and supercell. Representing various degrees of intensity and characterized by different weather patterns, each category of storm poses a safety risk to everyone in its path.

Single-cell thunderstorms (often referred to as pulse storms or ordinary thunderstorms) are the most common and are usually short-lived. They last only 30–45 minutes and typically produce brief heavy rain, lightning, thunder and light wind.

Multi-cell thunderstorms, meanwhile, consist of multiple storms that work together (like a cluster). These are more intense than single-cell thunderstorms and can last for several hours, producing heavy rain, hail and strong winds.

Squall line storms (or multicellular line storms) are known for their strong, damaging winds, hail and heavy rainfall. As their name implies, squall lines have a linear shape. These storms can stretch for hundreds of miles, and while they are rarely associated with tornadoes, they are known to produce wind speeds matching those seen in category 1 hurricanes.

Supercell thunderstorms are the least common but most severe type of thunderstorm. They have a highly organized structure, which allows them to last for several hours, producing very large hail, damaging winds and tornadoes. In fact, most violent tornadoes are byproducts of supercell thunderstorms, which can be present 20-60 minutes before producing dangerous funnel clouds.

Watch thunderstorm warnings

When the risk of a thunderstorm is high or imminent, weather services will issue watches or warnings. And it’s important to know the difference so that you can plan appropriately.

A severe thunderstorm watch means that approaching weather conditions could produce a severe thunderstorm. A watch can last for several hours and lets people in the affected area know about the potential for hazardous weather conditions. As the meteorological phenomena develop, an existing severe thunderstorm watch can be upgraded to a tornado watch. Tornado watches can be issued instead of severe thunderstorm watches when the weather indicates the potential for approaching storms that are capable of producing tornadoes. After that, they are upgraded to a tornado warning once the storm actually develops. 

That’s the key difference: warnings communicate a higher level of storm certainty than watches. A severe thunderstorm warning means that an existing storm of heavy rain and strong winds has a good possibility of turning worse, and a tornado warning means that a tornado has been spotted or is imminent and you should take cover immediately.

Thunderstorm myths

Thunderstorms are so common that a misleading mythology has developed about them. Many people talk about lightning “facts” in passing conversations, but some of the things people have been led to believe about thunderstorms are simply not true. These myths may be contributing to the widespread complacency around severe weather hazards.

Let’s dispel some of those myths:

Myth: Lightning never strikes the same place twice.

Fact: Lightning often strikes the same place twice. For example, the 102-story Empire State Building is estimated to be hit by lightning 25 times per year.

Myth: Lightning does not strike if there’s no rain.

Fact: Lightning may occur as far as 25 miles away from rainfall.

Myth: The rubber of car tires grounds you and protects against lightning strikes.

Fact: Rubber can act as an insulator at low voltages, but the voltage of lightning is too high for tires to offer sufficient protection.

Safety in the forecast

Your workplace should have an action plan for every type of emergency, including how to react to a severe thunderstorm. But these storms are a 24/7 safety concern, so it’s also important for employees to have a personal plan.

Regardless of where they are, they should follow the 30-30 Rule: When they see lightning, count the time until they hear thunder—if it’s 30 seconds or less, the storm is close enough to be dangerous. The advice is: “When thunder roars, go indoors and stay there until 30 minutes after the last clap of thunder.” If you’re hearing impaired, the rule to follow is: “If you see the flash, make the dash (inside)”.

Here are some personal safety plans that can keep people safe when the thunder starts cracking.

What to do at work

1. Follow the instructions of the personnel in charge of the emergency plan.
2. Move to a safe place in the building, away from windows and doors.
3. Stay away from items that may conduct electricity like computers, desk telephones and appliances.
4. Use battery-operated devices, like laptops or cellphones, instead of ones that are plugged into a non-battery power source.
5. Avoid using plumbing where possible—lightning will travel through metal plumbing.

What to do at home

1. Follow your home emergency plan.
2. Move to a safe place, away from windows and doors. Stay off porches.
3. Lightning can travel through metal wires, bars and concrete in walls and flooring, so don’t lean on exterior walls during the storm.
4. Stay away from items that may conduct electricity like telephones, televisions and appliances. If there’s time before the thunderstorm ensues, unplug electronics. Power surges caused by lightning can seriously damage your devices or even start small electrical fires.
5. Use battery-operated devices, like cellphones or flashlights, instead of ones that require power.
6. Avoid showering, bathing and other activities that involve running water or plumbing during a thunderstorm—it’s worth repeating: lightning will travel through metal plumbing.

What to do if you’re outside

1. If possible, go inside a sturdy building.
2. Avoid sheltering under trees, poles, wires, fences or anything else that might attract lightning.
3. Avoid bus shelters or any type of open construction.
4. If you are caught in an open field, do not lay flat on the ground.
5. Seek shelter inside an enclosed building or a hard-top vehicle when possible.
6. If you cannot seek shelter, kneel on the ground with your feet together, your hands on your knees and your body bent forward.
7. Water is an excellent conductor of electricity. Watch out for flood waters that fill low-lying areas. And be careful around creeks and rivers that may be subject to flash flooding during a severe storm.
8. If you are in a boat, get to land as quickly as possible and avoid swimming.

What to do if you’re in your vehicle

1. In order to be safe while driving in the rain, reduce speed, turn off cruise control, give space while on the road, and brake early for stop signs, traffic lights and other obstructions.
2. Find a safe place to pull over and park in a thunderstorm. Stay in the car, with your hazard lights on, until the heavy rains subside. Even though the myth of the rubber tires grounding you from a lightning strike isn’t true, it’s safer to be inside a hard-top vehicle—without touching metal surfaces—than it is to be outside.
3. Avoid touching metal or other surfaces that conduct electricity inside or outside the vehicle.

Now that you’re prepared for the next severe thunderstorm in your vicinity, spread the word and start dispelling complacency in your workplace. Print the guidelines in this post, or incorporate them into a toolbox talk, to ensure that your employees are safe in the event of a thunderstorm, no matter where they are or what human factors are present.