I used these boots for the month of October in the Alaskan arctic, mainly on barrier islands and sea ice. Temperatures were 0-25 degrees (fahrenheit) and we often had 5-15 mph winds. I was outside, crouching and mostly not moving, for 1-2 hours at a time. My feet did occasionally become cool, but they never became cold to the point of discomfort. These boots possess thick insulation, and a layer of waffled material under the foot, which must help trap warm air.One note - I wear about a size 9 shoe, and I ordered size 10 boots. When the boots arrived I almost sent them back because they felt so tight; however, after several days of use, the insulation packed out to a surprising degree and the boots now almost feel too large.