Catamaran and lightning: sailing safely

Encountering lightning at sea is rare, but not impossible. During the last Excess Campus, several owners shared their concerns with us: how should you react when facing a storm? How can you protect yourself? What happens if lightning strikes a catamaran? Rest assured, here is what you need to know.

Thunderstorms at sea: understanding the risks

Every day, around 4,000 thunderstorms occur worldwide, generating more than 9 million lightning strikes. Lightning hits the Earth’s surface on average 100 times per second. Ocean areas are generally less exposed than land, but coastal regions remain higher-risk zones. With climate change, the frequency of thunderstorms is increasing.

While the probability of being struck while sailing remains very low, the consequences can be serious. That is why understanding the phenomenon is essential.

Two types of thunderstorms to be aware of

Cyclonic thunderstorms are associated with tropical depressions, storms and cyclones. They form when warm, humid air rises and meets colder air fronts. They move slowly and can be tracked and anticipated using modern weather tools.

Thermal thunderstorms result from the rapid ascent of warm, humid air when the surface of the sea or land heats up intensely. They develop suddenly and locally, often near coastlines or mountainous areas. Within just a few hours, they can catch even experienced sailors off guard.

How lightning forms

Lightning occurs when electrical charges build up within storm clouds. The upper part of the cloud becomes positively charged, while the lower part becomes negatively charged. The sea surface beneath the cloud acquires a positive charge.

When the difference between these charges reaches a critical threshold, the air becomes conductive. A sudden electrical discharge then travels toward the ground, the sea, or between different parts of the cloud.

Why catamarans are affected

On land and at sea alike, lightning always seeks the most conductive point. On a boat, it generally strikes the mast or the highest metal components. Once on board, it looks for the shortest path to the sea: from the mast, the energy travels down through the shrouds, forestays, metal structures or underwater anodes.

Catamarans are mostly built using composite materials, which are poor electrical conductors. Without proper conductivity, lightning may seek alternative paths to reach the water, causing secondary arcs, power surges, and mechanical or electronic damage.

Excess systems designed to protect your catamaran from lightning

To prevent burns, internal damage or fire hazards, a dissipation circuit is essential. That is why all Excess catamarans are designed to channel electrical energy safely.

The Excess 11 and Excess 13 models integrate a bonding system between the mast, the central compression post and an immersed grounding plate. This defined pathway directs lightning energy toward the water without passing through sensitive onboard components.

On the Excess 14, which does not have a central compression post, the connection to the grounding plate runs through the shrouds.

Never apply antifouling to the immersed anode. It plays a critical role in grounding your catamaran.

Anticipating lightning risk on board

There are several ways to anticipate storm activity while sailing.

Before departure:

• Check the grounding system under the hull

• Learn how to read cloud formations

• Brief the crew on the procedure to follow in the event of a storm

• Carry a portable GPS so you can continue navigating comfortably if onboard instruments are disconnected

While sailing:

• Monitor weather updates to avoid crossing a storm system. Marine weather applications help track cyclonic storms and provide alerts

• If necessary, head toward the nearest port or closer to the coastline, which may act as a natural lightning conductor

How to react if a storm is imminent at sea

If a storm is approaching, a few simple actions can help protect both you and your equipment:

• Disconnect all non-essential electronic devices, especially those installed at the masthead (anemometer, wind vane, antennas, etc.)

• Switch off secondary batteries

• Avoid touching metal parts and remain inside the boat, dry and away from electrical circuits

• If appropriate, keep the engine running to avoid being left without power should the alternator or starter be damaged

Once the storm has passed, carefully inspect navigation lights, instruments, antennas and all electrical connections.

Storms and lightning at sea: share your experience with the community

Have you experienced a lightning strike while sailing a catamaran and would like to share your story? Have you modified your boat, or do you simply have questions on the topic?

Our collaborative platform, Excess Lab, allows you to go further. Join the discussion in the comments.