We've seen accumulated hours below freezing this weekend, as low as 10 degrees.
This soil thermometer is inserted into the ground 6-8" deep. So what?
In this region, there's no need to flush/ winterize an irrigation
system, short of turning off on the day of a freezing event to prevent the accumulation of ice
on plants and sidewalks. Always a good practice, prior to a low temperature event to maintain proper soil moisture.