Oh the number of times I was stuck in those leantos during rainy camping trips growing up. Big Deer and Stillwater have both been flooded by our family camping trips.
One time when I was in my early 20's, we were at Big Deer and expected a rainy Saturday. I woke up Saturday morning, looked out and saw beautiful blue skies. I was psyched! Then I realized it was merely the large blue tarp we had strung up from leanto over the picnic table. The rain soon started and didn't end until we started packing up Sunday morning.