The record low temperatures for various cities are as follows:

New Orleans: $\displaystyle {19}°{F}$

St. Louis: $\displaystyle {6}°{F}$

Houston: $\displaystyle -{2}°{F}$

Salt Lake City: $\displaystyle -{11}°{F}$

What is the difference between the warmest record low temperature and the coldest record low temperature?

°F.