I ride 90 miles round trip everyday to work.
From now until late september it can be pretty unpleasant.
It is expected to be 97 with about 80 % humity.
I tried a Veskimo yesterday for the first time and was impressed with it.
I had frozen 6 bottles of water and when I made it home they were all melted but the unit kept me nice and cool for the hour it took to get there.
I did not even sweat under my helmet. I suppose keeping my core cool helped with my over all heat.

I just thought I would post up that it worked.
I had been looking at it for a year wondering if it would work

 

Checked their website and wondering why the frozen water bottles would melt so fast. Back when I rode mountain bikes I used a Camelback hydration system, 100 ounce model. I would fill it with 2/3 ice and the rest water. I could ride all day and never run out of ice and it keeping at least my back cool. To boot it was black which of course attracted more heat. I think this company needs to come up with some better insulation. Not knocking it and glad it helps you but seems the frozen bottles should last all day and then some. A guy I ride with keeps frozen bottles in the tour pack of his Ultra wrapped in towels to drink. They stay good all day long.

 

The water circulating through the vest gets hot.
Returns to the cooler and cools off when it contacts the ice.
So you are kind of pouring hot water over the ice