Thresholds for Extreme Heat

Below are preliminary Heat Index (HI) thresholds for extreme heat*. These thresholds will be updated as more data become available.

Region NumberHeat Index Threshold (°F)
1101
2103
3102
4100
599
694
7101

*Appropriate region groupings for each jurisdiction can be obtained from the map below. Counties are grouped based on similar HI thresholds.