low point drains tank drain winterizing

went to drain my low point drains-there are four in the cubby-1 red 1 black near door-1 red 1 black farther back-red had warm water and so did the black-how do i turn my water heater off?? i've turned my alde heater on at 60 degrees-supposed to get down to 33 tonight so was going to drain my lines  also opened the water holding tank to drain and it has a bunch of water in it!! it was supposedly empty when i picked it up at the dealer and i have never put any water in it-i've been to some state parks that all had water hook-ups-i just left it to drain and went to work.  If i turn the hot water bypass valve will that keep water in the hot water tank? i don't want it to be empty if the Hot water is on and why is the water from the other lines feeling warm also??-I live in southern Louisiana and this early cold snap has thrown me for a loop-i didn't think it would get this cold so early-it doesn't usually-I don't think anything will happen with just a few hours of 33-34 degrees but wanted to be safe