Given that Tourer is in NC, I suspect he was asking about the frozen pack vests due to humidity...here in the South, there's a fair amount of the year where the humidity is 90+%, and evaporative cooling doesn't work all that well. Wetting one's shirt to cool off just means that you're hot...and wet. It'll work a little, but once you reach the wet bulb temp, you're as cool as you're gonna get. ........
I'm in WinstonSalem NC....and I can second the above. Evaporative cooling ceases working in late-May every year and doesn't resume until mid-October.
....sT
Journeyman ATCS, retired
U.S. DOT - Federal Aviation Administration -- 1982-2012
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