“In recent years, excessive heat has caused more deaths than all other weather events, including floods.” 

* Excessive Heat Watch – Conditions are favorable for an excessive heat event to meet or exceed local Excessive Heat Warning criteria in the next 24 to 72 hours.

*Heat Advisory – Heat Index values are forecasting to meet locally defined advisory criteria for 1 to 2 days (daytime highs= 100-105° Fahrenheit).

* Excessive Heat Warning – Heat Index values are forecasting to meet or exceed locally defined warning criteria for at least 2 days (daytime highs= 105-110° Fahrenheit).

Source: https://www.redcross.org/get-help/how-to-prepare-for-emergencies/types-of-emergencies/heat-wave-safety.html