@Tygrow78 you need to know the temperature of the air that is closest to the leaves. It’s the difference between the temp/humidity inside or just on the surface of the leaf, and the temp/humidity of the air that is blowing across the leaf’s surface.
VPD is a measure of the difference, or deficit like the D in Vapor Pressure Deficit, of the leaf and it’s environment. The bigger the deficit between the leaf and the wind, the faster the leaf can transpire and move water and nutrients up from the roots. Imagine if you were 100% wet, like you just got out of a pool or steam sauna (100% RH like the inside of a leaf), and stepped outside into a wind. If it’s a hot and dry wind you’ll dry off a lot faster than if it was a cool and humid day. The deficit between the surface of your wet skin (the leaf) is greater (higher VPD number) when the air is hot and dry. This is also true if we keep the air dry but change the temperature. The deficit is greater when the temperature is higher.
Wind is another important factor. Step outside with wet skin on a cold, windy, higher RH day and you might actually dry off faster than on a hotter, dryer day that had a slower wind. Wind affects leaves in the same way.