Freeze Skip Trigger Information

I was surprised to wake up this morning to see my Gen2 executed a freeze skip, mainly because my location has never recorded a freezing temperature. So I looked at my settings and saw that my Freeze Skip setting is 40F. I think this is reasonable for my area. If the nighttime temperature is this low there probably is not a need to water. The problem is that I looked at my reporting station KOXR (2 mi away) and the minimum reported is 44F. Where does the controller get the information to trigger skips?