This is the coolest graph I have seen today. Maybe this week. From retired UGA ag extension agent Rad Yager, who got this from a blueberry producer near Homerville GA. It shows temperature traces from two ambient air sensors plus one that was exposed to irrigation water used for frost protection last night. You can see the spike in temperature as the warm groundwater pumping was started (or else that was when he brought it into his warm truck to remove the cover), followed by evaporative cooling of the wet sensor. The pumping kept the temperature of the iced-over sensor all night near freezing while the air temperature plummeted. In the morning the sensor, covered in clear ice, warmed up inside its ice shell until enough water melted to make thermal contact with the sensor and the wet sensor got cold again until the ice fell off. Then the sensor’s temperature rose above the ambient temperature sensors because it was not shaded. Physics in action!