I already kinda dived into the idea on another board, but it got my mind buzzing...
How would you guys do it ya think? Here's my thoughts:
First off, I love OLC so I'd try to make this as OLCable as possible.
As we've all felt, the affects of weather on our bodies can change depending on many things. In the real life, what clothing we wear very much so changes the affect. Now apply this to a knight wearing cloth (very absorbant) armor in the rain, he'll weigh more and become tired more easily. Though some types of clolth become stronger when wet, thus a small boost to AC would be in order for those types. Other types, however, degrade faster when wet.
So with that said first - We'd have to implement some sort of material type for armor and clothing. I could also see benefits in this when considering other things, such as a more advanced elemental spell system. (metal armor + energy-based spell = Mage kicks ass )
Now secondly, we have numerous races. A sprite may find it very difficult to fly in windy weather, while a giant couldn't care much about the weather. A race with fur would find the cold a breeze, but a warmer climate would be hell. Thus we have a second variable that would need to be added. I'd call it a Racial climate RIS - What races resist certain climate types, are immune to them, or succeptable to them.
Then we can look at the benefits of spells and such. This means we should really calculate the Climate RIS of a character and store it on the pc_data It'd be hell to do it otherwise with these factors.
Now we have a way to tell what character will have what effect in what climate. Now we need a way to make the affects of a previous climate last if they need to. If you were just in a monsoon, you won't quite be dry by walking into a cloudy room. You would also dry faster if you walked into a desert. This is where something similar to the current affect system would be handy.
So far it seems simple, but how to make it all work?
The Climate RIS would be calculated when certain changes happen to a player. When armor is changed, spells are casted, or even when the 'race' of a character is changed (polymorph). An engine would have to take the current climate, and then the character's Climate RIS, and place a 'weather affect' on the player which will also affect the character's climate RIS. If you're soaked from the rain, and then it gets REAL cold and starts snowing... you're not going to feel too well.
So now we somewhat have a system in mind. But what will this do to players? That's an even trickier part I think. It can't be as simple as taking HP or movement, but that's a place to start. Perhaps weather affects could apply other affects, such as 'common cold' or the like.
Now with all this said... we have a working psuedo weather affect system. But is it all worth it? We just made playing the MUD 10 times harder and more hell for players. Sure it seems 'cool', but so did getting thirsty and tired at first. Then it was a royal pain in the arse.
On the flip side, there could be bonuses for certain weather conditions. Mages already have to wait for bad weather to use things like 'call lightning'. So further we could think about what benefits would certain classes get for certain weather conditions, and what penalties would they get? *boggle*
Well there it is, in gray and .. well gray, or whatever your colors look like!