I usually drain the radiator and block before it gets cold enough for that to happen. On my old car I couldn't get to one of the block plugs without pulling a header. I drained the side I could get to and got busy with other stuff and forgot about it. Sure enough it froze what little water was in that one side and cracked the block. This was a stock block and after I tore it down I found a problem with the main journals that rendered the block junk anyways so there was no loss for me on that one. With the way the weather has been this year I have had to drain my car after test-n-tune. 70s one day and freezing the next.