Weather (Not just clouds)

[RatchetinSpace]

I know clouds have been brought up a lot on this forum, but I think clouds are only half the story.

Weather is often a determining factor in the success or failure of space missions or aircraft flights, be it on Earth, or at the destination.

1. Wind - Wind plays a big factor when taking off or landing with aircraft. High wind speeds and storms also cause hazard for re-entering spacecraft, and for spacecraft wishing to launch.

2. Clouds - Clouds add a layer of uncertainty to approaches, as it is more difficult to judge where your spacecraft will touch down, (especially on a planet like eve where there would be very thick clouds). It'd also add nice aesthetics.

3. Rain - Again, mostly cosmetic, but adding another level of depth to the planets you are visiting. Every day is the same on the moon, but Laythe storms would add a different perspective to the mostly barren moon.

4. Storms - Storms would combine all of the above, not freak hurricanes which destroy ground bases (although poorly built ground bases or top-heavy landers might topple) but still a deterrence from landing.

Weather is something which is closely tied to aeronautics and space, and I think I'd be a loss if KSP didn't implement some form of weather system.
PS: No mod I've seen has successfully combined all of the above. I've seen Kerbal Wind: 

And I've seen EVE:

But these two do not represent a fully functioning weather system.

[Columbia]

The thing about this is, the effects would greatly bog down on performance.

[BadLeo]

Weather simulation implies a lot of other things, at least in my - amateur - view. The simulation of wind is, on itself, heavy on performance. Then there comes the particles that rain, smog and clouds will add to it. If it ever comes, it'll not the simplest thing to be added to the game.

[Anomalous16]

I like the idea and for those displeased by the idea an option can be added to disable dynamic weather like many games do 

[Jonfliesgoats]

Performance aside, weather would be a decent addition to the game.  Rain would add a small, but noticeable amount of weight to vehicles.  Temperature variation would affect engine efficiency for jets, rockets and props.  Wind on a large rocket would require more work from reaction wheels or even RCS to maintain a trajectory below the troposphere.

This all adds some common sense elements of consideration for vehicles that can just get into LKO with single-digit reserves of DV.