Relative humidity fall crocus
Jane McGary (Fri, 13 Aug 2004 19:10:05 PDT)

Regarding dew point, I have never heard this statistic mentioned on our
local weather reports, but they always mention the freezing point, which is
an elevation above sea level. In summer this can range from about 6000 to
15000 feet, roughly. (There are permanent snowfields and glaciers on Mt.
Hood less than an hour's drive from my house.)

My own land is at 1600 feet asl. Temperatures here are slightly cooler than
where Dave Karnstedt lives, which I think is about 150 feet. In addition,
there is more frequent wind here, owing to downslope winds and the
influence of a major river gorge (the Clackamas River, the one south of the
Columbia).

In addition, we mustn't forget the "urban heat island" effect. Pavement and
buildings act as heat "sinks" and release heat over a longer night period
than vegetated countryside. Nights in a city are hotter than in the
country. Certain topography can also affect temperature; for instance, the
little town of Estacada, 6 miles from my home, is regularly hotter, though
only about 700 feet lower, because it sits at the bottom of a narrow river
valley.

There are plenty more interesting things about small climatic patterns. I
had the opportunity to work as the copyeditor on the Oxford Encyclopedia of
Climate and Weather, and can look things up in it for anyone who is interested.

Jane McGary
Northwestern Oregon, USA
Finally cooling off a little today