Interesting side story I read a short time ago about breaking through the ice. This ice fisherman and his brother hit this lake near his house.
Here's the background. They had had a number of consecutive days near 10 degrees then a spike where it went up to 40 degrees. Optimum conditions for any guy wanting to fish through the ice. Long cold days providing plenty of thick solid ice, but nice weather to be out there enjoying it without freezing your butt off. This particular body of water was fed by a creek that ran between 2 slopes on one side of the lake. These slopes were covered with snow.
So the guys headed out onto the ice and spent most of the day enjoying the weather and the catch. They decided to head back before it got dark. On their way back to the truck, each brother began falling through the ice. One after the other. Every few feet. Each brother fell through 3 times before they finally made it to shore and got into the truck, shredding their clothes and trying to get warm quickly.
So why did the ice break after so many consecutive cold days? The creek. The snow on the slopes around the creek melted and the creek then fed this warmer water into the lake, directly under the path these poor gentlemen took to get to and from their fishing spot.
For those of you not familiar with safe ice, here's a quick reference chart.