On the weather quality group this is commonly observed along with a few degrees higher in dewpoint over surrounding stations. If not already, please sign up for CWOP and re-broadcast your weather data there. Great charts and graphs to determine the quality of your output and tools to compare to adjacent stations.
My station:
http://weather.gladstonefamily.net/site/C3833Sign up, all free and helps the weather guys digest data for running the models.
Since I am a weather nut, I was debating getting another station for down by the pond at the bottom of the hill so I could compare the two, but I am guessing a veto from the other half.
Note that our pond is near the end of the driveway near the road, so nowhere near the weather station. It doesn't show up yet on Google maps.
A few more things. This discrepancy is totally reliant on dewpoint of the air, air temperature, and water temperature of the pond.
For example if the water is colder than the dewpoint, it will extract moisture from the air, lowering the dewpoint when the air reaches the other side, but not necessarily the air temperature. This condition will raise water temp up to the dewpoint very quickly due to latent energy transfer of condensation but leaving the air feeling more comfortable.
If the dewpoint is much lower than the water temperature, even if the air is hot, the water may cool down from evaporation(pending solar energy addition) and will cool the air as well as it picks up moisture again leaving the air feeling more comfortable.
When the water is very warm and the dewpoint is similarly high, then your pond can have the reverse effect, making the air more sultry and uncomfortable. Example: Southern swamps.
