Mine free range in all weathers, even in the rain. Actually, if it's going to rain all day they will forage out in it, if it's only going to be a few showers, they take shelter. Their feathers should protect the rain from ever really reaching their skin, although some birds in molt may be a little less waterproof. They apply oil to their feathers from an oil gland at the base of their tail for this very reason..weatherproofing.
When I feed in the morning, during the winter months, all the feed is usually gone by around late afternoon around 2-3 pm. They still free range in the winter time and forage on the greens, even in the snow. When I fed dry feeds, there would still be just a skiff of feed in the trough the next morning...just some powder and a few grains. Now that I feed FF, there is never really much left over at the end of the day...they practically lick it clean.
I have found my birds just naturally eat less in the winter months as they don't move around nearly as much as they do when forage is good. I also cut the rations with whole grains in the winter to lower the proteins but add a little fats and fiber. So they actually consume even less calories in the winter, though almost the same amount of food...when everyone else is adding proteins to "keep them warm", I'm cutting them to keep them healthier and to save me money.
Chickens are opportunistic eaters, so if the easiest opportunity is in the trough, they will hang close to the coop for constant snacking, but if it isn't, they will range out and forage for foods elsewhere. My birds move out over about 2 acres of land when they forage, the CX birds went all over 3 acres.
I use a standard feed scoop like one you would find in pet stores and such, and I fed a flock of 30 chickens and whatever chicks were present around 4-5 scoops of dry feed in the winter months. In the warm months, it was 3-4 scoops. I have half that number now and I feed 2 level scoops of FF each evening and no more..even that is probably too much as they aren't as slim as they need to be. In the winter that may go up to three level scoops.
From what I can tell, the scoop I use is a 2 cup scoop...so my birds get 4 cups of FF each day for 14 birds and 6 cups of feed in the winter months. Now, the levelness of the scoop measure can go up or down as I am constantly tweaking just a bit, so that is not absolute and it varies a little with the seasons and the general condition of the birds. Sometimes I'll use heaping scoops and sometimes level scoops to regulate the amounts, when they are showing too much weight.
It's something you have to play with as you get to know your flock and what is "good condition" for them, but not too good of condition, if you know what I mean. The birds should always be hungry enough to clean their plate for the day...if not, then tweak it down until they get enough but are not leaving left overs.