I was using Vivid Weathers before and never had any problems with rain.

Now after two new playthroughs and roughly 40 hours of gameplay I've yet to see rain a single time in Climates of Tamriel.

There are times when the clouds are dark and you see and hear thunder/lightning in the distance, but still no rain.

Is this just the nature of this mod, or is something wrong with my game?

It's the only outdoor lighting mod that I use (RLO for interiors) and it was always on a completely new game without the data from the old mods.

I'm also using the usual Footprints, Wet and Cold, Cloaks of Skyrim, Wonders of Weather on top of it.

LOOT is handling the loadorder.

I've found some topics about it on Google, but none of it lead to a solution :/

Don't know what to tell you. I have lots of rain with CoT in my game. Rains pretty hard and I get wet and have to dry off (Frostfall). I am using CoT, RLO (dungeons only) Wet and Cold, Frostfall (version 2.6), and water WATER. No other weather mods besides CoT though.

Edit: Are you using AOS2? That needs a Cot patch and the version of the patch for CoT 5.0 is kinda hard to find. Using the old version of the AOS2/Cot patch patch with CoT 5.0 can mess up your weather cycles.

Rains in my game just fine, with CoT 5.0.

Same with my game. Lots of rain and snow where appropriate. I've been using CoT since it was released and just lately updated to 5.0 version for this runthrough.

no sound mods either

but it seems like I fixed it now after some more searching on Google ^^

I had to add

[Weather]

bPrecipitation=1

to my Skyrim.ini for whatever reason.

Waited a couple of hours and it rained ^^

See if any other mods changes Data\textures\effects\fxraindrops.dds. You may need to look inside some BSA files to find out.

I get rain and snow, though I would like to see a bit more than I get.

And sometimes I think there's too much!

Lots of rain for me too.