With the addition of The Mist to the halls of cinema, it's important now that everyone be educated on their atmospheric water masses and what to do when you come upon them..
A cloud is a visible mass of condensed droplets or frozen crystals floating in the atmosphere. Clouds can vary in size covering only a few blocks or hundreds of miles depending on the front. At their tamest, serious cloud cover can make you blue, ruining a good day of golf or a nice outing at the pool or beach. And while they might seem innocent alone by themselves surrounded by blue sky looking all fluffy like cotton candy and forming pretty things like dogs and castles, they can be a menace when they get together with their buddies. With serious clouds comes serious rain and lighting. There can be flooding and lightning can kill with a direct hit or possibly hitting a tree that might come crashing down on you or on your house, causing your house to collapse on you and kill you.
With heavy cloud cover, seek protection in your house, a building or under a shelter somewhere.
Fog is a cloud that comes in contract with the ground. It can cover several miles in all directions. Whatever you do don't go into the fog dammit. Listen to me again. Stay away from the fog. The fog contains lepers. Lepers that are pissed and they have hooks and shit and big swords and the lepers faces are all gnarled and have worms coming out of their sockets and these guys will kill you because these mothers are vengeful.
If you see the fog run away because the fog covers ground fast, filling city streets in a matter of seconds. Seek protection between your legs where you can kiss your ass goodbye because the fog comes through open doors and underneath doors and through window cracks and those damn gaping holes in houses that you were supposed to take care of last week and told your spouse that you would take care of but instead you went and saw the game with your fellas and hopefully that was one hell of a game because now the lepers are coming in through that gaping hole to kill your ass. The only hope from the fog is that the people or relatives of the people who originally pissed off the lepers make peace with the lepers and by peace I mean they let the lepers kill them. Once that happens, the fog will disappear and you can live a somewhat normal life that now consists of the knowledge that fog carries lepers.
Mist consists of small water droplets suspended in air. Like fog, mist can cover several miles of ground. When you see mist, do now gawk and kill the urge to snap pictures as the pretty mist comes down from the mountains and creeps its way towards you. Stay the fuck away from mist. Mist is evil and bad and it usually means that the military has unlocked a portal to another time and dimension. A time and dimension where giant bugs fly through the air and if they sting you you'll swell up and die and gigantic spiders shoot acid covered webs and giant cockroach like things walk amongst us and they'll rip you apart if the gigantic monster like something or others with tentacles hanging from their belly don't get you first.
When you see the mist don't decide to catch up on some grocery shopping, unless that grocery store is 100 stories below ground. You know what, screw that idea. Grab some food, dig a hole, climb into an all metal box with a little straw for oxygen, throw the box in the hole and cover yourself up until you hear a tank or something because that means that the military has resealed the portal and successfully killed off most of those nasty sumbitches so that you can once again live in peace until the portal opens back up which could really happen at any time so honestly, once you see the mist, your life will constantly be filled with dread.
The differences between fog and mist are subtle and whatever you do, don't get caught debating the intricacies of the two because you'll find yourself killed by a leper or a giant bug and shit, let's hope that the fog and mist don't meet and hook up because then you would have to fear a leper riding a big bug trying to kill you.
Hope this helps.