Dewrag: Hi I also have the ws2310 weather station. I thought I had the same problem except it was the indoor humidity dropping to 19%. I went out and purchased a whole house humidifier and now it responds better indoors. I have seen the outdoor humidity also drop down to 19% on a couple of occasions. The book says that when the humidity drops below 20% it cannot register and defaults to 19%. It usually recovers. What I did is I just purchased another weather station and replaced both the main unit and the thermo-hygro unit and it made no difference. Unless I have two bad units or it is an inherent problem with the ws2310. I will return the other weather station for credit now that I have tried both. Let me know what you find out from Lacross… Thanks Dave…