Often in games we have a tendency to overlook some of the basic concerns of being alive. We run our characters like machines. They sleep on command, they eat whatever is available for nourishment, and we just leave the less savory details to be glossed over in the background. It works perfectly fine for the most part, but there are opportunities to be had with some of these mundanities that it could be fun to bring up in your game from time to time.
A Horrible/Great Night's Sleep
Ever have a horrible night's sleep? How did the next day go for you? I'm going to guess fairly miserable. You were probably a bit snappish with people, a little down, and had an aura of "just leave me alone" that close peers disrespected at their own peril. You ever have a bad night's sleep in a RPG? No? Well, why not?
Now, obviously, there are some things going in your usual adventurer's favor to help them sleep. Walking all day, for one, tends to help let people sleep fairly well. However, that doesn't mean that bad night's can't happen, or that they can't add flavor to a game session. By that I don't mean mechanicaly penalizing combat rolls - we're not talking exhaustion levels of fatigue here - but maybe have a small, but hidden, penalty on some social rolls or just hone in on how things seem worse because of the poor night's sleep. It's not "it starts to rain," it's "of course, then it starts to pour down on top of you." Just a small touch, but one that can carry meaning.
On the inverse, if you are plaguing your PCs with bad night's sleep, it is only fair that they sometimes have a great night of sleep. You know the type. The kind of sleep where you wake up the next morning and there ain't nothing in the world that you can't fix. This is the kind of thing where it could be good to give a small mechanical bonus - particularly to morale type checks.
Run with it, and your players will probably pick up on it too. Anyone interested in RPing their character will likely enjoy the chance to portray their character on a good day and a bad day to add depth to th character. Others may not, and that's ok too. It's still worth feeling out.
Armor Is More Than A Tactical Concern
One of the most common requests I get from players is they want to sleep in their armor. This usually follows with a small argument/discussion about how practical/impractical it is to do that. Chain is a pain to sleep in states the person with real experience trying it. The rules say you don't benefit from a long rest if you do says the person who is checking the mechanics of it. It then boils down to sleep is a moment of vulnerability for the fighter because he can't have his heavy armor on, and in a fantasy world isn't it strange that my bad ass soldier turned adventuring warrior can't sleep in his armor and benefit from a rest?
In L5R the crab clan's Hida family has a technique that states they receive no penalties to checks for wearing heavy armor. The fluff implies they're always in it. I've had arguments with players and GMs about whether or notit means they can sleep properly in armor, from both sides depending on the game.
Ultimately, I don't have a problem with someone sleeping in their armor (unless I'm specifically running by the book and the book has a problem) but there are consequences to that action that may be more than mechanics. Like what? Well, consider for one how someone who lives, fights, eats, and sleeps in their armor is going to smell. Ever wear the same pair of shoes for a prolonged period because they're the only pair you have? Even with time out of them, they can get pretty rank if not cared for properly. Now imagine a fighter walking miles each day, fighting, under the sun, and sleeping in their armor day in and day out for a week long journey. At the end, that fighter is going to be pretty smelly, and that could cause issues next time the person is in town.
The weather is rarely used as more than a plot point in stories. When was the last time it rained on your party and not because someone cast a spell? When was the last time your players had to deal with a foggy morning/evening and weren't ending up being transported to Ravenloft? Have you ever used weather as more than just setting a mood for a location or score of events?
If so, how? If not? Why not?
Now, granted, weather is hard to keep track of and can be a lot of book keeping, but it is a part of life and one that is so often glossed over despite the depth it can add.It can be used as part of a luck mechanic (hey, it's raining pretty heavily today, so the ferryman isn't bringing people across the river) or just as something to add to a scene (you wake up the next morning to the sound of children laughing and your breath misting in the air. Apparently it snowed last night.)
The point of all this is that life is full of a lot of fun details that never make it into game, but those details can add to your game. So why not give them a shot and see how your group likes them.