That fence is not what I'd hoped. The area is too wide to be easily covered and it is not high enough for that anyway. A 4' high chain linked fence will not stop many predators, a lot of critters can climb over it or just jump it. If you properly use electricity that becomes a formidable barrier. Even critters that can jump it usually check it out first and just leave when they get shocked. Without electricity it may work OK during the day but the nighttime risk is pretty high. There is still a risk during the daytime, practically any predator will hunt then. I've seen bobcat, coyote, fox, dogs, and even raccoon hunting during the day.
Where you are I would expect you to see snow and temperatures as low as zero Fahrenheit in winter, at least occasionally. The temperatures don't both me that much, I've seen chickens sleep in trees in weather colder than that. They were in a protected area out of wind but with all that great ventilation they did not have trouble with frostbite. Still, you do not want to build a coop that funnels wind to where they sleep, that would be dangerous. They need wind protection and ventilation when they sleep.
Snow and a cold wind present other problems. Chickens don't like change. When they wake up to a white world they often will not go out in the snow for a few days. I have an area bigger than yours that would have grass sticking up above the snow. After a couple of days some would go out foraging, but not all. But for the first couple of days they would not venture out.
A cold wind is also a problem. Mine went outside in temperatures below zero F if it is calm. If a cold wind is blowing they stay out of it. You will probably have some days they will not want to go outside even if there is no snow. If that area is set up so there are wind blocks to stop a cold breeze it is a lot more usable in cold weather than if it is just open to the wind. I'm not sure how much of a problem wind would be for you. I think most days your chickens will be able to get outside in spite of the snow and cold wind, but you will probably have times they can't.
Chickens do not compartmentalize their thinking about space to "this is coop" and "this is run" like humans often do. When they need room they look at how much room is available regardless of what we might call it. I'd hoped to be able to come up with a relatively inexpensive way for you to provide a sheltered area for sleeping and nests to keep the nests dry and have a predator proof area they could access when they woke up. I don't trust your winters enough to recommend something like that. If you were further south it would be easier. For 20 chickens I'd suggest something in the order or 8' x 12'.
You can try finding free or inexpensive buildings or building materials on Craigslist, which you will probably have to move on your own. You can ask at construction sites if they have scrap materials (often they use lumber for construction aids, such as forms to pour concrete and then they are trash to them), or maybe check out Habitat type stores for inexpensive windows, doors, or hardware. Then build something suitable. Or reduce the number of chickens to what you can manage. You can perhaps expand in the future.
