>>201978Depends on the season, as usual. A light wool blanket or fleece is usually a good idea no matter what in addition to the bivy. Of course I don't carry these everywhere, only when I'm doing a out and back dayhike that takes place in decently remote areas.
First priority is to stay dry. You stay dry, you can stay warm, you stay warm, you can stay alive.
I did wilderness SAR in the Cascades, and 90% of the deaths I saw were not due to falls or other mishaps, it was due to going on a hike on a nice day up in the hills wearing cotton street clothes, getting caught in a rain-storm, temps dropped to around 50f (as they do quickly at altitude) and boom, hypothermia in 20min or less.
Seriously, I've pulled all manner of people, alive and dead, out of the mountains for the same reason, the wore cotton, they got wet, and they didn't realize that you can die of hypothermia when its 65f outside.
