I spend a lot of time outdoors. I may be a geek/nerd but I like being outdoors and actually spend time outside. One thing that rarely stops me is the weather. Because of this I can end up outside in the rain or during a blizzard. This is a big reason I only buy archive grade and water resistant inks and papers.
I'm also "me" and I'm usually good for rising to "hold my beer" moments that won't result in another trip to the hospital trauma ward.
Being able to write and/or take notes on paper during a torrential downpour was one of these hold my beer moments.
This post distills the results.
In short: very few writing instruments are going to work in the rain and wet.
Stick to the basics or things made to be water proof. For waterproof writing I'm fond of wood pencils, tactical pens that take Fisher Space Pen cartridges (CRKT / Gerber), or 2mm lead holders. The Fisher Space Pen cartridge ink is water proof and pencils or 2mm leads are basically waterproof by design. Some leads / pencils aren't waterproof but are very rare in practice.
The Rite in the Rain notebooks tend to surface on military sites and use a wax coated paper. I have many of these notebooks and prefer them when I need a durable paper that can survive a lot of water and crappy environments.
The Field Notes Explorer notebooks are made of synthetic paper. The pages do NOT tear out, are waterproof, fire resistant and a hell of a lot more. Check the specs, they are impressive. Think indestructible. They are also super smooth to write on. So much so even the Fisher Space pen ink will smear at times. This is a pencil or sharpie notebook in my opinion. It's not the best for me but definitely a notebook to try at least once.
Time To Write
I wish I had more to say but there are very few options for analog writers that spend a lot of time outdoors and need durable supplies. Doubly so for those that deal with wet environments and rain.
Hopefully this has helped despite the lean amount of options available.