The Muck "Woody Max" may be the warmest boot for its weight I've seen.
They are relatively light, comfortable, and good walkers.
HOWEVER, they are not very durable if you need to walk thru a lot of green briar and/or heavy brush. The rubber bottoms are fine, but the neoprene uppers are easily punctured. I like mine, just saying the upper portion is easily punctured, even more easily on some of Muck's lighter-weight boots, such as the "Ranger", "Fieldblazer" or "Wetlands" versions.