Yesterday's lightning strike at Hamilton North School, which left four injured, came as a dramatic reminder that thunderstorms can sometimes be as dangerous as they sound.

On average, New Zealand receives around 187,000 lightning strikes at sea and on land each year.

While that was a comparatively small amount of strikes, incidents did happen here.

Some notable cases have included a Northland man who was killed, along with his horse, in 2011 and two Waikato men who were struck in 2013.

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In April this year, a 9-year-old girl was pulled her from her bedroom by her parents seconds before lightning split a huge tree outside sending a branch smashing through her window.

Shaken by the near miss, the Te Puke family went outside to find their dog dead, believed to have been electrocuted by a lightning strike.

Lightning was caused by the discharge of electricity from thunderstorms and could occur within a cloud, between clouds, or between a cloud and the ground.

Parts of the West Coast in the South Island had the highest annual average density of ground strikes, up to 40 per 25sq km a year.

Parts of the Taranaki, Waikato, and Bay of Plenty regions were prone to lightning, with an annual average of up to 16 ground strikes per 25sq km a year in some areas.

So what should we do in a lightning strike or a thunderstorm?

On average, New Zealand receives around 187,000 strikes from lightning at sea and on land each year. Photo / File
On average, New Zealand receives around 187,000 strikes from lightning at sea and on land each year. Photo / File

The best place to be during a severe thunderstorm was in a sturdy building – and among the worst were gazebos, rain or picnic shelters, golf carts, and other isolated structures in otherwise open areas.

Items such as golf clubs, fishing poles, tractors, bicycles and camping equipment acted as natural lightning rods.

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Civil Defence advised we should pick a safe place to gather in our homes, where there were no windows, skylights, or glass doors, which could be broken by strong winds or hail and cause damage or injury.

We should also bring our pets indoors, shut windows and close outside doors securely, unplug and then avoid electrical equipment and telephones, and also steer clear of bathtubs, water taps, and sinks because metal pipes and plumbing can conduct electricity if struck by lightning.

If there was no reinforced building in sight, the best thing we could do was take shelter in a vehicle, keep the windows closed, and avoid touching metal.

If we were already driving, the safest move was to pull safely on to the shoulder of the road and stop, turn the hazard lights on, and make sure we were away from any trees or other tall objects that could fall on the vehicle.

As a last resort, and if there was no suitable structure or vehicle available, we should move to a low-lying, open place away from trees, poles, or metal objects – and one safe from flooding.

Civil Defence recommended we crouch low to ground on the balls of our feet, while placing our head between our knees – this minimised our contact with the ground, as lightning currents typically entered a victim through the ground, rather than by a direct overhead strike.