In extreme high temperature or high humidity days, reducing the Humidex speed setting during peak hours will help to reduce the load on the AC unit; specifically when the dew point temperatures are higher.
Considering the house is sealed up during AC operation, it creates a negative pressure and could potentially allow air infiltration through wall cavities. You can resume normal operation during evenings and overnights when the dew point temperature is attainable.
**Except for southern climates, this method is generally used for 2-4 weeks until heat wave is over, when normal Humidex operation can be resumed.