You have to remember that most sloughs are shallow, and the water heats up quicker on those. Most lakes have deeper water and therefore don't loose ice as fast (water stays colder). Snow has a lot of effect on ice also, heavy snow will weigh down thinner ice and push water up through the ice, plus snow acts like a layer of insulation and keeps the colder temps away from the ice. Here around Minot when it was warmer temps awhile back we really didn't loose ice it just got a little soft and became a crappy layer on the water. I'm going fishing Sunday and will still be careful, as I always consider ice unsafe no mater what the thickness is.