Please be assured that a 20 degree bag is more than adequate in Yosemite Valley or the Sierra Nevada backcountry this time of year. No need to lug around a huge 0 degree bag.
Yosemite Valley forecast for this weekend indicates a low of around 42F and @27F in the high country above 10,000 feet.
If, for some reason, he gets cold in the 20 degree bag, he can always add layers of clothing.
Not to worry mom!
Last edited by Bob West; 05/13/16 02:02 PM.