I am a lot farther north than you, and opened yesterday. In the event of freezing temperatures, I just keep the pump running overnight. As has been said, it's far preferable to look at a nice clear pool than a leaf and dirty water-covered winter cover. As well, you will open to a relatively clear pool, instead of a green monster, and you have a few weeks to balance the chemicals, fix leaky pipes, and shake down the equipment before the warm weather hits, and you are hit with a hot day, anxious kids, and a pool that's not quite ready. As well, if pool equipment repairs/replacement are needed, the lineup at the pool store is much shorter right now than it will be on Memorial Day weekend!