Specifies how weather index units are to be calculated.
Average
The cumulative number of weather index units for each day in the calculation period divided by the number of days in the calculation period.
Maximum
The maximum number of weather index units for any day in the calculaiton period.
Minimum
The minimum number of weather index units for any day in the calculaiton period.
Cumulative
The cumulative number of weather index units for each day in the calculaiton period.