I think what is generally done is they are taken out, placed in a paper bag or
cardboard box in the fridge (you want something breathable not a sealed container), then after all threat of frost has passed they are put out to hatch. This is to mitigate some of those early warm ups in the spring that are followed by a cold snap...that unpredictable spring weather can be devastating on the little guys! Another thing to do would be to put the bee house in a spot that stays cold longer in the spring (i.e. a frost pocket, north facing slope, etc.), you don't want them waking up too early is the main idea.
