Oh we considered actual visual weather, but the amount of lag it causes is just not worth it. SL just isn't robust enough for such thing.
Not even some very basic light particle plates with a few dozen drops of rain scribbled on them or something?
-Bea
Unfortunately, no.
There are several reasons we don't have particle weather as particles or as 'prim plates'.
For particles, one such reason is that SL renders only a limited particle count & it prioritizes which particles to render poorly. The result of this is that, for instance, because we have particle torches and particle waterfalls in Lismore, the number of particles that your client renders has already filled up the buffer by the time you load into the sim (unless your draw distance is really low). So if the particle rain starts when you're in Lismore, you still wouldn't be able to see it until you zoom out past the sky walls that surround the islands which will trigger SL's occlusion culling and de-render the islands until you zoom back in again. That will empty the buffer & the particles closest to you will render until the buffer fills up again.
In short: even if performance wasn't an issue, the way SL renders particles in the world makes it hugely impractical since more than likely you aren't going to see the rain until you consciously try to make it visible...in which case the whole purpose of having rain particles so that people have a clearer indication of rainfall when it happens, is entirely defeated.
Another couple of reasons we don't have particle rain are because it generates sim lag, and also because most players playing Second Life apparently still use 7-9 year-old rigs that crash or burn out horribly when they have to render particles, so these players turn their particle density down to 0 (or to a really low amount) which again defeats the purpose of having particle rain in the first place.
So far as static weather plates with animated textures in the sim went, we experimented with that already but couldn't find a way to do it without inadvertently disabling clicking in the world. The prims simply got in the way of the mouse, and interfered with everything from clicking to moving your camera around.
Summarized, it's simply impossible to conveniently & reliably simulate weather conditions visually in the SL game world with the currently available tech. It's something we would like to do, and I'm pretty sure that we will if it becomes possible in the future.