Two years ago, one of our heifers, Josie, gave birth in the middle of the night during a March snow storm. At daybreak, we found her calf in the field near death. After calling a friend for advice, we ran to the local farm store and bought a calf coat. I wrapped the calf up, loaded him into the bucket of the tractor and drove him to the barn, with mama following close behind. After 12 hours wrapped in the coat, lying in a warm and dry barn with his mama and a tube feeding of colostrum, the calf started to gain strength.
Josie was a willing mama, but having her in the head gate made holding baby up easier. These weak calves tend to have trouble standing on their front feet. After a day or so of assistance, the calf was able to stand and nurse normally on his own.
After this experience, I keep a calf coat on hand for early spring or late winter births. The extra warmth of the coat can make all of the difference in saving a calf born in cold, wet weather.