Heat indices get exponentially wonky when the dews get high. There's going to be higher dews over the vegetative/wet areas though. The Davis sensors may be a little high, but the dews definitely pool from evapotranspiration on these dead air heat days.
My dew hit 82F earlier...but I usually only post here the lowest dew I record in the previous 15 mins or so. Like my dew is 78F right now, but it recorded 75F twice in the last 15 mins so I'll call it 91/75. Jives more with the ASOS sites.