NFPA 22 Lowest Mean Temperature for one day?

[BatesEngineer]

How does one determine the Lowest Mean Temperature for one day? I am trying to determine if heating is need for a fire tank and NFPA 22 does not give a clear direction.

The location in question is Bainbridge, GA which is in the southwest corner of the state.

Thanks in advance.

 

[UFT12]

check ASHRAE fundamentals.