Open year long and at $6/person per night, Camp 4 is my go to for winter camping in Yosemite. As an added bonus, the entrance to Upper Yosemite Falls Trail connects directly to Camp 4, making it easy to wake up in the morning and get a heads start on the trail.
This campground also operates on a first-come ,first-serve basis so be sure to get there early. I`ve only been during the winter season, so whenever I stayed the campsites were never full. However, I would recommend getting there as early as possible to reserve the best spots(apparently people wait in line from 5AM during peak season).
There are 35 shared walk in campsites equipped with a fire pit, a bench or two, and 4 shared food lockers.
There is also a campsite bathroom with flushing toilets and toilet papers(no showers though). Im not too sure about other times throughout the year, but during the winter the bathrooms are heated (a lifesaver in the early mornings when the sun isn’t out yet).
There is also free parking available for people staying at Camp 4. Parking permits are required during spring through fall.
This campsite is apparently popular within the rock climbing community and features the Columbia Boulder, an iconic boulder with challenging bouldering problems.
When I visited in mid February, the snow from the valley was beginning to melt so most of the campsites were spotted with puddles of water and most (if not all) of the ground was wet or covered in snow.