Upgrade your T/H sensor to the new SHT-31, which is more accurate than anything Davis has ever used. Scaled Instruments has these pretty cheap and they work in 2005+ ISS that accept digital sensors with a minor calibration adjustment. I’ve picked one up and so far I like the response and accuracy especially on the humidity side.
See also the WXforum post for discussion - http://www.wxforum.net/index.php?topic=29036.0.
Here is the Davis bulletin:
[color=navy]In early 2016 Vantage Pro2 systems will switch to a new temperature humidity sensor with new and exceptional accuracy specs.
This new sensor requires new transmitter firmware to communicate with it properly. As a result, you will see on your new 2016 Replacement Parts Price List that there are new and old temperature humidity sensors as well as new and old transmitter boards.
The new Temperature Humidity sensor is much more accurate than the prior sensor.
New Temperature Humidity sensor spec