A proper kilt will not come to any harm from the rain-even when worn all day out in continuous heavy rain and for that matter the next and the next.

Certainly it is kinder to the wearer than trousers-or for that matter waterproof trousers for the rain.

In my younger days-I did a lot of backpacking in both the UK and Scandinavia--lands where it can rain and rain and rain-so I can speak with some little experience. This includes river crossings where I and the kilt were in waist deep water.

So you'll be a lot better off than any trousered companion.

James