Obviously water freezes at 32 degrees. But as always it's not that simple. A cup of water outside for 2 hours at 32F isn't going to freeze. That same cup of water at -5 for will probably freeze pretty quickly.
The question is, at what temperature should we start being concerned for water in LU to freeze and start doing damage? I ask this because last night it got down to 30 degrees. Day time temperature Saturday was 54, high of 63 today. The boat was in a non-insulated enclosed storage space. Most of the water was drained out, but there was maybe less than a cup left when I checked this morning. I'm not too concerned because it should've been at least a few degrees warmer in the storage space, and I don't think it was cold long enough. But interested to see what you guys say.