Dear Tom,
What exactly do you mean when you say temperatures are below or above normal? Please define “normal.”
Dan MacGregor

Dear Dan,
In meteorology, a normal temperature at a specific location is the temperature obtained by averaging the daily midnight-to-midnight, standard time, high and low temperatures at that location during the 30-year period 1991 through 2020. New temperature normals are recalculated every ten years. The next period will be 2001 through 2030.

The recalculation is performed to take into account the gradual changes in climate that are occurring. Precipitation normals and the normals of all other meteorological variables are calculated using the same time period.