From a quick google search it looks like there has been some talk about that model over on the Sandysoft forum. However, that's all I see and to be fair most of it is linked to the Cumulus software.
If you want to check it out, just pop the following into Google: Watson W-8681-PRO site:sandaysoft.com
For your temperature readings I've not seen that problem with some of the local stations that I look at around here all of which report in metric.
I'm sure someone with some more experience with Weatherunderground might be able to help/add some more information for you.