I hunted with 400 grams for about 5 years and just put on thicker socks in the colder months but not to thick to cut off circulation. I stepped up to 1000 now and those are WARM!!!. I say split the difference either 600 or 800 grams should easily get you through the colder months. It doesn't really matter on the warmer days cause if you do a bunch of walking or anything your gonna sweat in any type or weight waders you have.