This will expose my not being the sharpest knife in the drawer, but I survived the experience obviously. I lived in Montana back in 1973&74 scouting and hunting Bighorn Sheep in the un-limited permit areas northeast of Yellowstone Park. I carried an 8'x 8' sheet of nylon thread re-inforced visqueen and would fold it over like a sandwich with my pad and sleeping bag inside, weighing down the edges with rocks which there is a never-ending supply of in the Beartooths. I usually spent the night at timberline with my "camp" under the edge of some bitterbrush. I would now splurge on one of the excellent light "bivy" tents available today and in fact I am applying for a draw permit in MT. this coming year, who knows? Another thought, even though I'm sure global warming is probably just a rumor, when I was there at the elevatins I was sleeping at even in July/August I expected precipitation at night to be snow , such is not the case today and makes a tent an even better idea.