Thunderstorms and lightning: protect your construction site and workers

In the summer, severe thunderstorms can sneak up on you at home or while camping. It’s a different story at construction sites: you must anticipate them. Dangers associated with strong wind, rain and lightning can be a serious threat to both people and equipment.

Managing these risks takes time. Get ready now with a proper emergency plan. We’ll review it with you!

What are the risks?

Severe thunderstorms produce extreme conditions: heavy rainfall, wind gusts, hail, lightning... Here’s an overview of the dangers they pose to equipment, structures and, of course, workers:

Here’s an example

Polythene covers building openings before windows are installed. During a storm, bad weather rips it apart and water begins to damage material.

On the same worksite, a drywall delivery just went south: while a hoist was lifting panels to the 3rd floor, strong winds blew them away; the impact caused some other minor, yet preventable breakage.

  • electrical surges, power outages, fires, electrocutions
  • falls for workers from up high

Real lightning strike: nothing like what you see in the movies

Lightning can carry up to 1,000,000 volts - more than enough to cause serious burns and cardiac or respiratory arrest.

In Canada, lightning kills more Canadians than hail, wind, rain and tornadoes combined  (This hyperlink will open in a new tab).. In 2021, Environment Canada reported lightning kills 2-3 people a year in the country and injures 180. Those who work outdoors are especially vulnerable.

With few exceptions, these accidents occur between April and October and most often in July after intense heat.

Risk management: get ready

As severe thunderstorms are a real safety concern, it’s not possible to wing it! You must have a prevention plan adapted to the size of your worksite. The larger the site, the more help and action needed to get it ready.

Here’s an example

Patrick has been overseeing a project for more than a year. Temporary power lines provide power to his office trailer and the ongoing construction.

Patrick questions the sturdiness of two of the poles that supply power to the construction site. The on-site engineer confirms that they won’t withstand strong winds. A specialized company will therefore help to stabilize the poles before something happens.

The following steps can be adapted to your situation and needs, but every one of them plays an important role.

1. Track thunderstorms

You’ll notice the sky darken, plus wind and temperature changes shortly before a thunderstorm hits. There’s still time to act and protect the worksite and workers as best you can, but nothing replaces actual weather-based planning.

With this in mind, assign a person who will be responsible for monitoring daily local forecasts and who can notify your crews in the event of an approaching storm. Their ‘weather watch’ can be performed in several ways, with your own sensors or a lightning detector. There are also websites and free online services, like the Map, which is updated every 10 minutes.

On the off chance you don’t have access to accurate information, thunder can give you an idea of how far away the lightning is. Thunder rumbles when lightning is in the distance; it makes a dry clapping or cracking sound as lightning gets closer.

2. Prepare a plan - this is the way out!

People can become disorganized or make poor decisions in an emergency. Keep them safe with a clear emergency plan.

If a violent thunderstorm is in the forecast, shut down work to protect your workers. Evacuate the area, restrict access and keep an eye on what goes in and out. Everybody, including you, should move immediately to a lower risk area.

Worse than altitude sickness...

Lightning tends to strike elevated points and things that conduct electricity well. Crane operators and labourers who work high up are particularly exposed to this risk, as well as to high winds.

Evacuate them asap. If ever a crane operator (for example) doesn’t have time to get out before a thunderstorm hits, they must shelter in place and touch nothing. People working nearby should leave the area without delay. Workers on the ground are also susceptible to electrocution or injuries caused by a collapsed crane.


Determine meeting points, wherever possible, one or more places to safely gather in the event of a thunderstorm.

  • Make sure to pick a closed building with plumbing and electricity. If lightning strikes, the current will first move through wiring and conduits, then the ground.
  • Avoid trailers or temporary shelters (hut, covered picnic area, etc.) that aren’t safe.
  • In the absence of a safe building, ask workers to shelter in vehicles parked away from trees, scaffolding, poles or any tall structure.

To protect themselves from lightning, everyone should also...

  • stay away from water or any object that conducts electricity (for example a metal fence)
  • keep away from conducive items in buildings: sinks, pipes, baseboard heaters, landline phones, etc.
  • avoid touching a metal surface or wired device (like a steering wheel) in vehicles
  • take shelter for up to 30 minutes after the last thunderclap

3. Establish procedures to secure material, equipment and, as always, your crews

Managing thunderstorms doesn’t mean simply evacuating the premises in case of danger... You also need to think prevention: set up procedures to explain how workers can keep themselves and the worksite safe. A wind gust at 60 km/h or more can pick up and violently toss items. You wouldn’t want to be in its path!

Here are some examples of items to cover up:

  • practices to adopt

    For example, when a thunderstorm is approaching, nobody should start or carry on with a task that cannot be stopped on the spot.

  • Criteria needed to suspend or resume work

    Will a code or alarm be used?

  • ways to protect material in the event of heavy rainfall and strong winds

Material should be secured to prevent injury and damage, ideally in a building or under heavy-duty tarps. Some equipment can be strapped down using ropes, chains, stakes, etc. Plan ahead!

4. Establish bang-on communication

People at the worksite should know how to protect themselves at all costs from lightning and hazardous conditions.

  • Provide information and, ideally, training on how to recognize the risks associated with severe thunderstorms.
  • Share evacuation and prevention procedures.
  • Introduce them again every year on every worksite. Confirm that everyone understands the procedures in the same way.
  • Implement a safe communication protocol so people who work remotely can stay in touch with each other and pass on emergency instructions.

What about your commercial insurance?

In addition to actions taken to protect people and your worksite, well thought out commercial insurance can help you address the risks.

Check if you have the required coverage to deal with any damage caused by a severe thunderstorm. If you’re good to go, keep an eye on the weather; we hope you can carry on with your work in the best possible conditions!