It is safer to be wet than dry in a lightning storm: Science

Lightning strikes are not a phenomenon to take easy. They can deliver currents in excess of 200 kiloamperes – far, far higher than the power required to kill a human.

Scientists have some important news for those of you who have a terror of getting struck by lightning: dousing your head in rainwater may increase your chance of survival by up to 90 percent!

That's the conclusion arrived at by a team of scientists who built fake human heads, zapped them with powerful bolts of electricity, and measured the results. The fake heads that had been soaked in water featured significantly less damage and lower internal exposure to electrical current.

The phantom heads undergoing lightning tests. (Technical University of Ilmenau)

The experiments conducted provided practical evidence for the theoretically postulated effect that rain-wet skin might have better lightning strike protective behaviour than dry skin.

More than one study has suggested that water may reduce the effect. Theoretical analysis suggests that wet skin could reduce current exposure to the body, while another study found that wet animals survived lightning strikes more frequently than dry ones. 

The wet head had fewer, and less severe, 'injuries' than the dry one; that is, regions that were damaged by the electricity to which they had been subjected.

And we have more information:

The electrode array also measured the currents running through and over the surface of the two heads. Now, when lightning strikes a person, that person can experience something called a surface flashover. The surface flashover is a discharge path on the surface of the skin caused by a high voltage difference between the entry point and exit point of the current across the body. Most of the lightning current travels along the flashover, and very little enters the body.
The results showed that a fully formed flashover happens whether the head is wet or dry. However, for the wet head, significantly less current entered the head; specifically, the energy that entered the brain cavity was 32.5 percent lower for the wet head than the dry one.
This reduced current exposure to the brain, combined with lesser physical injuries, could greatly enhance a wet person's odds of survival, by up to 70 to 90 percent, the researchers said.

The best chance you have of surviving is not to be struck by lightning at all – but if you do find yourself caught out in a storm, with no shelter available, you could do a lot worse than drenching yourself in the rain, the research suggests.

https://www.nature.com/articles/s41598-023-50563-w