The Mississippi hatch is unbelievable. The highway dept gets out the snow plows to push the dead mayflies off the roads.
They like the bright lights of gas stations.
Here are radar images centered on LaCrosse, Wi. In the upper right of the first image, you can see the city of Steven's Point which is about 30 miles to our south. My city is not labeled.
Until you have seen a major hex spinner fall, you can't imagine how heavy it can get. And you can't catch a fish because of how many naturals there are.