Reduce risk of harm from electric storm in hot tub in covered area
As I read your question, you're looking for protection against a lightening strike during a very rare electrical storm. I'm going to assume you're looking for personal protection more than full on protection for your house/electronics/etc - things can be replaced, people, not so much, but that protection for the things would be a definite bonus.

I live in the Midwest US. 99.999% of the electrical storms we get (and we get a lot of 'em) come with rumbling thunder from distant lightening long before we get any strikes anywhere near us. When you hear the thunder, party's over - get out and move inside. NOW! Watch the show from a window if you want to watch. (I'll often watch distant lightening from our covered, generally dry front porch, it can be quite spectacular! But, once it starts getting close, I head inside.)

Some &quot;pop-up thunderstorms&quot; do happen. Those are the 0.001% not covered above. Just get out as quickly as possible and head inside.
If a strike really does come out of nowhere and hits your house/pergola/hot tub, there's really not much you can do about it.


Install a properly grounded/earthed lightning rod on the top of the house/highest point around. A proper lightning rod (system, more than one rod may be necessary) will most likely attract most of the strikes that come near your house and will properly dissipate the charge into the ground instead of you, your house and your electric devices.