Living in the PNW with many consecutive months of damp and cool weather, I've found most humidity sensors to be unreliable. Often their operating range is between 20% and 80%, which misses the very dry summers and very wet winters here. After a few weeks, I start getting bad readings, and finally failures.
Lately, I've had better results using a small 5VDC fan within the weather station enclosure, with the hope that dew won't form on the sensor (probably the main culprit). It's a Silicon Labs Si7021 temperature and humidity sensors (I2C). So far so good.
Yes, they do fail. I guess that's evident by the design of the weather station, as the humidity sensor is modular, so it can be replaced.
Unfortunately, I think this design also means it has a low ingress protection value. The unit I ended up with had the humidity sensor replaced and it still wasn't providing numbers. I think it may have spent a year or so out at sea on a buoy.
