It may be mid October but temperatures are still in the low 90's in the Valley of the Sun. Some Phoenicians are brave enough to still venture into the less than warm water to splash about in one of the estimated 615,000 pools in Arizona. If that seems like a lot of Marco Polo, consider that there are over 10.4 million residential pools and 309,000 public pools in the United States. ( That's about 1 pool for every 30 people ). Cannonball !