"Matt Barrow" wrote:

Yes.

What's that got to do with your made-up statement that the temperature was
104 F. and the humidity was 90%?

How was that made up? Check the weather records from June, 1990. Do a
google
search on heat related deaths in Chicago.

I meant the part about 90% RH. If you look, you'll see that's off the chart
at 104 deg. F.

Did you attempt to understand the chart?


Yes, and I understand your point, thank you. I assume your point is that
one
would perspire more at 120 than at 104. If so, that wasn't my point.

No, my point is that 90% RH at 104 deg. F. is not a set of conditions one
will find in the surface atmosphere. People often assume that the humidity
is much higher than it actually is when the weather is warm. At 104 deg. F.,
50% RH would be awfully uncomfortable; 90% RH would be, if not impossible,
damned near it.

Relative humidity is the humidity you feel. Given constant absolute humidity
(no front, rainstorm), the highest relative humidity occurs at the coolest
part of the day, usually around dawn.

One thing...When the desert gets how it still cools substantially during
the
evening and night. When humid air gets hot (like the 104-105 that Chicago
had, the heat effect holds. I suspect that a couple days of this is what
kills so many and did back in 1990.

The heat holds because of the high dewpoint. The dewpoint acts as a low
limit to temperature fall because of the heat of condensation--as atmospheric
water condenses it gives up heat and warms the air. The higher the dewpoint,
the higher the overnight low. Cloud cover can also affect this by slowing
radiaton cooling.
--
Dan
C-172RG at BFM