We Calve in March and April. It can be pretty nasty and cold or it can be really nice...
Here's a picture of our setup...
Our calving routine is (if the weather is nice and there are no issues)
1. cows are sorted about once a week to pull the heavies off, they are then put in the Main Calving area
2. They stay there until they are calving/or have calved.
3. Once the calf is around 24 hours old (we catch them when they are up and moving around, sleeping calves don't move very well) the are brought up through the barn yard, tagged, weighed, banded, etc.
4. They go out into the Maternity Area, where they will usually stay til they are between a week and 2 weeks old.
5. They are then kicked out into one of the bigger pastures, where they will stay until the pastures are ready for them. We will usually have a calf shelter where they can get out of bad weather if they need to.
If we have issues at calving, (mothering, weather or calving problems), the cows will be brought into the barn and dealt with and once the calf is up, dried off and going good they will be kicked out with the other pairs.
If the weather is nasty (I'm talking blizzardy or really cold (below 25 or so F), we keep them in the barn as long as possible, and if we do have to move them out to bring new cows in we only kick them out in the middle of the afternoon, when it is as warm and nice as possible. We will double them up in the stalls, or keep the calves in and kick the cows out and rotate them back in for the calves to suck if needed. Usually once they've had a few hours to dry off and have sucked good several times they are pretty tough, and our Maternity Area has a couple of calf shelters and an area where only the calves can get in, it faces the south and is very sheltered.