I know it has been awhile, but here is the update:
I originally purchased two SHT35-DIS modules. Along with writing code to emulate the ISS, I also wrote stand alone code for them. They have been running for months, one with a filter and one without. I am convinced that they both exhibit the same "wetness" that the other Sensirion sensors do. I guess that given that the spec sheet states the following:
The sensor shows best performance when operated within recommended normal temperature and humidity range of 5 °C
– 60 °C and 20 %RH – 80 %RH, respectively. Long-term exposure to conditions outside normal range, especially at high
humidity, may temporarily offset the RH signal (e.g. +3%RH after 60h kept at >80%RH). After returning into the normal
temperature and humidity range the sensor will slowly come back to calibration state by itself.
The results I got are to be expected. The above quote applies to the newer SHT85 as well. Maybe it is just in the packaging, my inexpensive AcuRite doesn't do this!
My results may seem disappointing, but all of my time wasn't wasted. The same concept could be applied to any other sensor whether it be analog, I2C or other. I/we just need to come up with a sensor that truly works well outdoors.
Maybe the HYT series is worth looking into.....