I wore the Moab Ventilator Mid in Fallujah, Iraq for 6-months during spring and summer. The temperature was almost 125-degrees on the hottest days. The Moabs kept my feet dry from perspiration and performed well on all types of terrain including gravel, sand and asphalt. I also use them for working out at the gym, including walking on the treadmill! I'm returning to Iraq or Afghanistan within the next 60-days and I have ordered another pair of the Moab Ventilator Mid, because Merrell recommends them for both hot and cold climates. I give the Moab a 5-star rating for use in extremely hot & dry weather (if I deploy to Afghanistan and they also perform well in cold & wet weather, I'll give them a 6-star rating).