The update to rain is great, but as I stood there in the editor, I realized I didn't *feel* like I was in the rain. I think the best way to improve the immersion of rain, with the lowest demand on computers, it to simply improve the sound effects.
When its pouring rain, you have to shout at the people next to you just so they can hear you. Right now the sound loop for rain is like a light drizzle, not a downpour required for higher levels of Rain (like over 50 on the slider in the editor).
Frankly, the worst part is the thunder (or what is trying to pass as thunder). When lightning shoots across the horizon, it shouldn't have this weak "crack" but instead of this low, rolling boom that sort of creeps up on you. With lightning at 100 on the slider, I've seen some fairly large strikes of lightning and only hear a creak, like someone opening a rusty door. I know the lightning we see is in the distance, but it should still bring power with its thunder. When you see lightning, you should hold your breath in anticipation for the roar that rolls over the hills. Instead it just sounds like one of your mates is eating a cracker.