#1 Turn the breakers off to the pool equipment. The last thing you want is an uncontrolled re-start when the power comes back on (you won’t know in advance). If the pump comes back on (or tries to), and ice has formed in the equipment or pipes you could have big problems: burst pipe, burnt out motor.
#2 With the breakers off, you should consider opening up any equipment: drain plugs, filters, chlorinator caps etc to give the expanding ice a place to go.
#3 After you get power back up, it will still take time for frozen pipes, filters, & pumps to thaw. It won’t be instantly when it reaches 33 degrees, you may want to wait several days, and then do a controlled start up.