Campsite Near Summit Lake East Of Piute Pass 11,300'
Sharon Bracing Against The Wind
A friend once observed, “You have an amazing ability to discern the obvious.” My obvious conclusion it that in the high Sierras backpackers have to consider and pack for the fourth season year round. I have viewed many YouTube articles by various self appointed gurus on lightweight and ultralight backpacking. The next worst thing other than having to stay overnight as a day hiker is finding yourself in the ‘fourth season’ with three-season equipment. The fourth season in the Sierras is based on elevation and the inevitability of storms.
For example, I often hear on YouTube that a 40-degree sleeping bag is both lightweight and adequate. I assume bag ratings are arrived at near sea level. 40 degrees is not the same at 11,000’. The human body does not process oxygen as well and the blood does not circulate as well. Oxygen saturation in the blood drops and heart rate and respiration increase in response. This serves to bring even more cold air into the body.
I was part of a SAR search party dropped off by helicopter in Crabtree Meadows along the JMT in October a few years ago. We slept on the ground in bivys with pads and sleeping bags in addition to the rest of our gear. The temperature dropped to below freezing that night. One deputy told me in the morning that he was cold during the night in a zero degree bag. I had two 32-degree bags (one inside the other) and was warm but not toasty warm. Others complained of the same problems.
I was stationed in Fairbanks Alaska in the Army and had to undergo winter indoctrination with a maximum overnight temperature of minus 25 degrees required (below zero!). We used double mummy bags and slept warm. My son had a 32F degree bag in McClure Meadow (9,700’) and slept cold at the end of June.
Sierra Storms can come up at any time and they can move in fast. The next thing you know is that the shirtsleeve weather you were hiking in is cold and the trail is covered in 4 inches of hail. Being wet and cold in the high Sierra can quickly lead to hypothermia. It takes a warmer bag to warm up again than it takes to stay warm when you are dry.
My point is simply this. High altitude affects the body and makes cold conditions worse. Storms at high altitude can bring about rapid temperature drops. In the interest of safety, accept the additional weight of a warmer sleeping bag IF you plan on sleeping at higher elevations. I have a Mountain Hardwear Phantom 45 degree bag for summer at low altitude but I use a Phantom 15 degree bag for summer at high altitude. Ice formed on my bear canister last week overnight in Center Basin (11,200’).
I am not suggesting that you carry crampons in summer but consider how the altitude negatively affects the body and the possible stormy weather too. Some consider a 15-degree bag at the low temperature end of the three-season bags but it is a good ‘winter’ bag in the summer in the Sierras.