In western Washington we have an ASOS site at Whidbey Island Naval Air Station (KNUW) whose temperature often runs considerably higher than surrounding sites.
For example, the high temperature today about 2 miles south of KNUW ASOS on Whidbey Island was 52 F at OAKH2. Similarly, the AgWeatherNet site on northern Whidbey Island near Coupeville had a high temperature of 52.4 F. But at KNUW ASOS the high temperature was 5 deg F warmer at 57 F.
At 2 PM PDT today (22 Sept 2015) the temperature at KNUW was running about +3 to +4 deg F warmer than surrounding sites as shown by this map.
It would be interesting to understand why the temperature at Whidbey Island NAS often runs so much higher than at surrounding sites.