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.

Cheers and stay cool...however you best can.