I had my dark lager lagering in my garage at 30 ± 2 °F for the past week. Well, we hit a brief cold spell here in MN. Nothing too bad. Highs in the 20's, lows in the 0's.
Bottom line... My lager froze. It wasn't too bad. It was more slushy than solidly frozen. I put it inside where it will sit until the temps get back to a nice comfortable 30-35°F range in a few days.
Strangely, my pilsner which is also in my garage has not shown signs of freezing...yet. Maybe the EtOH concentration is high enough :)
UPDATE: oops, now the pilsner froze. I should not be surprised. It was -5°F at 8AM this morning. I should have been a bit more proactive. I knew it was going to get really cold, but I pushed my luck. Oh well, it is almost ready to be bottled anyways. I may need to add some yeast to ensure carbonation. I'm not sure if enough yeast will survive the deep freeze.