Weather

It's a pretty under utilized mechanic, and I think I understand why. It largely only provides penalties, and gives the feeling of being nickel and dimed while creating yet another thing for the DM to track.

I think there's bound to be a way to create some pros as well as cons. I'd love to hear some other thoughts as well. I think rangers could become a whole lot more interesting as a base class if their skills helped mitigate these sorts of effects, too. Or even added benefits based on weather.

Supernatural weather effects could open up a lot of things as well, up to and including bonuses to charisma checks in sunny weather, as a gift from the gods.

Just spit balling. 

Any weather effect that reduce normal capacity is bound to be negative, wether it hamper vision or movement. But it can often be helpful in some ways, for exemple there could be advantage to tracking in heavy mud or snow etc 

It’s kind of like darkness in that it can work for you as much as against you. If it’s harder to see or hear enemies approaching, it’s also harder for them to see and hear you. Also, if you have call lightning prepared, a stormcloud is your friend.
Beyond that, it can be nice flavor. It helps set the scene and makes travel more than “you got there.”

Yeah it's all penalties, but it is penalties to enemies as well. You could house rule to have enemy disadvantage represented as player advantage. Like instead of enemies having disadvantage on perception, give players advantage on stealth, etc.

Weather effects with no penalties or benefits: Aurora (northern/southern lights), rainbows, sun-dogs, the green flash, sun rays. Smoke and dust in the sky can change the sun's color red or blue.

Rain doesn't have to cause penalties if it is light enough.

Beneficial weather effects: Looming is an atmospheric refraction effect, that extends visibility while over water, making objects just over the horizon appear above it. Gives advantage to perception checks for finding far away ships or land while on a boat/ship.