Maj. Kevin Eilers (right), bio-environmental engineer for the Kentucky Air National Guard’s 123rd Contingency Response Group, demonstrates how to use a wet bulb globe temperature apparatus to Master Sgt. Peter Vicini during Operation Lone Oak at Volk Field, Wis., June 9, 2021. The apparatus takes temperature readings to determine work-rest cycles during certain weather conditions, which became crucial for safety during an unprecedented heat wave over the course of the exercise. (U.S. Air National Guard photo by Senior Master Sgt. Vicky Spesard)