53.8 degrees on Oct 31 when we closed the pool. We normally don't keep it open during October, but expense-wise, the extra month wasn't bad at all. We used 8 extra kWh this month compared to last year, and the chlorine demand dropped to where I only had to add a bottle of bleach every three days instead of every day. We didn't add any stinky "winter conditioner" to the water this year either, and I can't wait to see the water quality when we open next April. For that matter I can't wait for April just to open the pool again . . I miss it so much.