I'm going on the Hell's Canyon Run in eastern Oregon from Tacoma Wa. in a week and it's been cold and rainy here in the NW and I'm assuming it will continue. I had a Yamaha 650 30 yrs ago and the seat foam would fill up with water in the rain, so I had to keep a garbage sack bungied over it. If I didn't, every time I would sit on it for a couple weeks after I would get a butt full of water.
I have 2 seats for my '03 Dyna...a Mustang touring seat and the stock Harley seat. Any rain riders out there know if they will leak?

 

Mine (stock Street Bob seat) lets a little in but we don't see near as much rain as you do.

 

Mine lets some in when I wash it, luckily it dont rain here hardly at all, so i dont notice it..

 

I live in the UK, and I keep my bike outside all year long. My seat has never held water.

 

I have a mustang touring seat and have been in some very heavy downpours with no issues.
I was going to respond that your leaky seat sounded like a personal problem but figured maybe not for your first time. Lol. Welcome.