Snow--assuming it's not to the point you can't walk in it--will sometimes produce very close flushes. Pheasants scattered around in heavy grass covered with snow: You'll often need to give them a boost with your boot to get them to flush.

On the other hand, when winter weather pushes pheasants into pockets of cover like cattails, you need to use a stealthy approach. Otherwise, the first pheasant to flush is likely to trigger a mass exodus. And you might need a 10ga to do any good if it happens when you're too far away.