On 2009-06-23, JPG wrote:

It always amazes me how mid-20s dewpoints get into the heartland of
America considering the distance from the sea. I realise that air
originates in Gulf of Mexico with 25-30 C SSTs but there seems to be
no loss due to the usual condensation processes (rainfall, dew).

I think you'll find the exceptionally high RH experienced in some states
is down to irrigation/crops evapotranspiration, particularly corn. (just
what I've read, I'm not an expert)
--
comp.john