Thunderstorms are extremely violent weather episodes. The risk of being struck by lightning is very real. For small boats, the risk is lethal.

Although the best thing to do is not to go out in stormy weather, what should you do if you are caught in a storm?

What behaviour should you adopt when faced with a storm, depending on whether you're sailing a liveaboard or an open boat?

Habitable boats

Habitable boats on day trips should avoid being at sea in stormy weather. Check the weather forecast to avoid any surprises.

• In the event of a storm, the safest position for the crew is in the cabin. 
• If you have to stay on deck, make sure you wear shoes with insulating soles, plastic or rubber soles capable of insulating your body.
• If you have an oven or, better still, a microwave oven on board, these are two very pretty Faraday cages capable of protecting your smartphones, portable VHF, satellite phones and portable GPS receivers, devices that will probably still work if lightning strikes the boat....
• Disconnect electrical and electronic equipment from its power supply as far as possible. 
• In particular, remember to disconnect the VHF antenna cable.
• Start the diesel engine. If you are struck by lightning, its ECU, starter motor and alternator will be out of action and they are difficult to disconnect in an emergency.
• Physically disconnect the batteries; circuit breakers will be useless in the presence of very high currents.
• If you're at anchor and you have this type of equipment, connect heavy gauge cable. 
• If you're at the marina, disconnect the power from the dock - it would be a shame to get your power surge from there.

Open boats

Small boats generally have no lightning protection. The risk of lightning strikes is tenfold on these boats, which should not be taken out in stormy weather. 

If you're careful, you check the weather forecast and don't go out in stormy weather.

• The first precaution is not to go out in a thunderstorm.
• If you're at sea when the storm breaks, go home.
• Don't stand on the T-top or balconies.
• On an open sailboat, do not touch the mast.
• Keep away from the outboard motor, which is a large metal mass at the stern.
• Try to make yourself as small as possible and ask your crew to lie on the bottom of the boat.
• The less you stand up, the better it is.