It doesn't do well in situations like today. For example, I have measured .59" with my Davis weather station, and only .06 with the tempest. The wind is probably off also due to the restricted air flow from ice, but I don't have anything to compare it to since my Davis station is frozen up.
Rain measurements have always been off with my Tempest station. Often more than 50% compared to my Davis and simple manual tube type rain gauge that I use.