As I shared in a recent post, Vapor Pressure Deficit (VPD) is an index that translates into plant stress. The darker the color in these illustrations, the more stressed the vegetation is. The more stressed, the more available to burn. While these levels vary from day to day, overall VPD levels have been on the rise in recent years.
Utilizing VPD to better characterize the fire environment is new to many of us. It describes fuel conditions in ways similar to fuel moisture and ERCs but because it is an absolute value, it will better reflect the impacts from climate change. I am updating this fairly regularly during August and September to help build reference points and improve an understanding of trends relative to this metric and the fire behavior we see.
*Map times are UTC, 7 hrs ahead of Pacific Time in the US. These maps are showing 5pm on the date prior to the image heading.