Labor Day weekend on the Canadian border can get PRETTY nippy!
And a 4 man rainfly on a 6 man tent doesn't protect quite enough. A few of my campmates had a LONG 4 days before we were due to be picked up again! (Soggy sleeping bags are NO fun and impossible to dry!)
I was bowhunting elk in Idaho one time in early October. I was planning on a short swing through an area which sometimes held elk. It was mid-morning, a nice warm day, and I was going to within a hour of truck the whole time, so I went out dressed in fairly light-weight cotton camos. In five minutes, it went from sunny to dark clouds. I'd never seen a storm roll in that quickly. Then the clouds opened and I got soaked to the skin. By the time I got back to my truck I was shivering uncontrollably. I know that is a sign of hypothermia but I figured I could make it back to my truck and I did. (I did have waterproof matches and firemaking materials, so I could have stopped and made a fire.)