After verifying that the dew point sensor at the Moorhead Airport automated station was operating properly, it has been determined that the 88 degree F dew point temperature recorded from 7pm to 9pm July 19, 2011 is the Minnesota state record for highest dew point temperature. The previous dew point temperature record was 86 degrees F set at Pipestone and St. James on July 23, 2005.
Note: at the time the dew-point reached the record 88F, wind speeds were decreasing and the air temperature rising. This suggests there were local influences that helped drive the dew-point to this extreme level.
For the curious or technically inclined, an in depth investigation of the sensor at Moorhead can be seen here.