Richard Ferguson wrote:
I have read somewhere that you can add up the air and water
temperature
to determine the degree of hypothermia hazard. What I don't remember
is
the range of total temperature that was relatively safe vs. unsafe.
I
did some google searching without finding what I was looking for. I
did
find some survival time tables as a function of water temperature,
and
one reference that said you should wear a wet suit if either the air
or
water temperature is under 65 degrees F.

I don't see where air temperature is really a factor for this, since it
can have a high variability and only some relation to water
temperature. You can check out some sites on Web sites at sites or
gages with air and water temperature. The two are related at times for
natural streams, especially at the extremes, for very cold and very
warm periods. But where the water temperature is effected by other
factor, glacier runoff, rain, snowmelt, and the ever-present dam
releases, the two aren't well related.

Some examples in Washington State a

http://waterdata.usgs.gov/wa/nwis/uv..._no= 12056500
http://waterdata.usgs.gov/wa/nwis/uv...te_no=12058800

The first is above a reservoir, the second below, at slightly different
elevations but not significantly for many cold days.

Interesting thought, but questionable application.

--Scott--

Scott M. Knowles "Opinions expressed are entirely my own."

Hydrologist, MS-Geography

"All things merge into one, and a river runs through it."
- Norman MacLean