I"ve been working overseas for a while now, and at 140+ degrees everyone sweats. The best boots i found,most comfortable, is the "original SWAT" line. Available in black or tan they wear well, and withstand a beating. AVOID the Timberlands and Danner as they are thick-heavy boots and sometimes take a year to truly break them in (DANNER).
I have high archs in my foot so i hafta supplement some extra padding, but with 130lbs of gear on it gets blasted pretty quick, so i always have extras in my kit. I'm not " gellin like magellan** haha Dr.Scholls commercial" but ive been using other inserts for the boots.
You may want to fit-test a couple boots from "Merrill", I recently just switched to those as a trial thing. GOOD footwear, comfortable (for the high archs too) but even to me they seemed a little warm (granted its still 100+ temps). So, im wondering is it the shoe or the ambient radiation of heat from the surfaces im walking on.Anyway,....try the Original SWAT line, they've done me good, and my sweat tends to be like acid to even the BEST socks (underarmor etc). Good luck!