AZT LASH SOBO – What Set Up to Be Warm But Not Hot?

If you expect sub-freezing weather, then some kind of pants might make sense. You didn’t say whether your rain gear includes pants; that might be enough for occasional cold snaps, since you have both leggings and a base.

A yard of alpha direct is cozy and multi-functional*. Can be worn as a serape, or easily made into a vest by adding snaps in front, arm holes, and connecting shoulders (again with snaps). It doubles as a blanket layer or a shawl for camp. (That’s why I suggested snaps instead of sewing the shoulders.)

Worn as a serape with your Sun hoody over it, it becomes an instant base layer; both warm and highly breathable.

AD is just fancy fleece; it’s maybe slightly warmer than 100-weight fleece (but weighs 1/4 as much). A linear yard (36×60 inches) rolls up to about the size of a 1.5 liter bottle. That might seem huge compared to your puffy, or even a down sleeping bag, but it is pretty versatile. You can’t wear your sleeping bag as a base layer. :)

(*) (credit to Mark Verber for the idea; he used AD as a poncho liner for his Camino trek).

You said that cold is a fear but do you sleep cold? I’ve spent many nights out in October north of the Mogollon Rim (near the end of your hike) and have rarely had a bottle freeze. (April I have had bottles freeze many times).

I have spent all of these nights in a 20° HG Burrow and an Xlite pad (except when hanging in a hammock which would add an HG Phoenix instead of thr XLite). I am a warm sleeper (I usually sleep in my hiking (short) underwear and a light baselayer up top.

My point here is I’d go with the 20° quilt unless you are a very very cold sleeper.

Disclaimer: I have not spent time farther up the AZT save for a couple nights near Flagstaff. Are their sections colder than the Rim (which is around 7500’)?

Rain is not uncommon in October. I’ll echo the question above regarding rain gear.

I worry about holes in my XLite. Just my $.02: I think it is worth bringing a CCF pad of some sort, either thin or short.

I have a Gossamer Gear 1/8 pad to help with the potential of xlite problems. My rain gear is not pants, but a rain skirt.

The North Rim sits around 9000 feet and there is one section just north of Flag that gets that high, but once you drop below the Mongollon Rim the highest is around 6500 feet in the section I will be doing.

A skirt/kilt and long gaiters are a credible replacement for pants in most conditions. Especially with your two layers of base+leggings.

“Warm but not hot” is mostly about breathability and flexible ventilation. As a general rule of thumb, fleece and windbreakers breathe much better than rain gear and puffies. While moving, I use combinations of polyester (either wicking or fleece depending on temperature) and wind shells in all weather except for too-warm-for-a-shell or heavy rain.

I think of hiking in the East as low altitude — basically near sea level. Most of the mountain West is much higher.

Air 6000 feet above sea level has about 80% of the molecules as sea level does; so cool conditions feel warmer than near sea level. (A partial vacuum bottle effect.) If you take 70 degrees F as a neutral skin temperature, then 2 degrees below freezing at 40 degrees lower  feels like 32 lower at 6000 feet. So 30 degrees at 6000′ feels like 38 degrees at sea level.

On the other hand, in open country winds may be higher in the fall than in the more densely treed East. The comparison in cooling is again proportional to the number of molecules impacting you per minute. Wind gear neutralizes wind. I suggest you pack your fears accordingly — with a focus on wind.

My feeling is that it is a bit difficult to address questions like this over the internet. Everyone is different and there is no substitute for firsthand experience. You know yourself best, and most likely you will need to be a bit conservative in bringing warm gear until you have spent more days and nights in the mountain west. Weather and conditions are variable, and it takes years to really feel that you know what to expect.

Sometimes I think that the through-hiking culture, social media, satellite communications, etc. make remote mountain terrain seem so accessible that people may not really appreciate all of the challenges that can be encountered, especially in the mountain west. I’m not referring specifically to the OP here, and obviously it’s always good to seek out advice. But IMO, it’s ok to expect some trial-and-error, and in fact, it can be very enjoyable to learn things that way.

Layers… if you take one too many layers, you can take one off and you are not too hot. But it you take one too few and your are too cold, and then you are miserable… or even in danger.

Just skimming some AZT SOBO blog posts, lows in the 20°F’s and cold winds are mentioned.  Often there’s not much blocking the wind.  Also the nights will be longer, with colder mornings. It’s only a 2 oz difference between your 2 quilts so maybe split the diff with some more wind-protective choices that can be worn as sleepwear in a pinch?

Good thing is a number of northfacing climbs will have ample shade.

Everyone sleeps different… I can be cold in a 20F bag at 40F, depending on how tired I am and other things. But sometimes I take the warmer clothing options instead of the warmer bag, figuring I can wear all those warmer cloths in the bag if necessary… There is a bit of an art to making those choices…

The information about molecules/elevation related to temperature is really interesting.

As for those asking if I sleep cold – I don’t know if I actually sleep cold or not, to tell you the truth. I just like to be warm when I sleep!
There is the chance to send layers home if I need to when I hit Pine, since I’ll be off the Mogollon rim at that point. At this point (still far out) they are calling for 45 degree overnight lows in Flagstaff the week that I will leave. Still iffy though, I don’t want to be in a bad situation if I have snow.

Any other opinions are appreciated, planning (if I remember) to report back here on what my final choices were and how it panned out.

“…molecules/elevation related to temperature is really interesting…”

Sure… but… if you are not acclimated to altitude you  may not yet have enough red blood cells to process enough oxygen to stay warm… you need to burn oxygen to be warm…. :)))  My experience is that I am colder at altitude, not warmer… yes, colder than one would expect for that same temp down lower… but also tired after hiking all day, so that makes a difference too… I would not ‘bank on’ being warmer at the same temp as at a lower elevation… a lot of variables…

DWR, your experience is not mine.

It takes a while to learn to pace for sufficient oxygen. (Humid air has fewer oxygen molecules at a given temperature.) While one can go up high for a day hike, it takes a few days to adapt to altitude — and being low on iron makes adapting much harder. So pacing can vary from day to day.

I live at sea level and prefer to hike on foot or ski high. Also, I live in wet country –western Oregon. While I have been altitude compromised at times (experiences in Idaho, Colorado, Wyoming and Oregon just flashed through my mind) I do not remember any experience of air temperature that did not follow the partial vacuum rule. Even when calibrated for being cold and wet at the same time.

I do not remember any experience of air temperature that did not follow the partial vacuum rule.

Could you be more specific about this rule? Is there an equation or chart that you are referring to? I am familiar with various calculations of apparent/perceived temperature, that take into account actual temperature, humidity, wind, and even sunlight, but I am not familiar with the scientific basis for the effects of altitude / air-density on apparent temperature.

Obviously the actual temperature does decrease with increasing elevation, but I am assuming that you are describing something more nuanced, since you suggested that a given temperature feels warmer at altitude than at sea level. This could be due to lower humidity or increased solar radiation, but I’d like to understand the idea that air density itself influences perceived temperature.

Steve S… and your experience is not mine….. of course, all 8 billion people on the planet can say that… so not saying much…

I don’t know much about your rules and formulas… all I have is a meager 50 years of experience hiking and living at altitude… so I guess you know more…

Dan, during the 1970s I ran into the original study in the library, perhaps by the Navy, that measured clothing needs under different conditions. Having started my mountain travel in the east, I was at that time adapting to the Oregon Cascades. I noticed during that period of adjustment that I usually needed less clothing at a given temperature at altitude than where I lived. Since dealing with wet was frequent all winter in both environments, it did not affect the observation. I had trouble mapping that study on clo measurement to my experiences, so my curiosity was aroused.

The breakthrough toward understanding came when I realized that the original study was done in one lab and ignored altitude. Wind chill charts and clo measurements still do.  See, for example, https://www.weather.gov/safety/cold-wind-chill-chart and https://roastsurvey.com/blog-post/understanding-clo-values/ and https://comfort.cbe.berkeley.edu/. However, in every case the measurement involves the transfer of heat to (for purposes here) colder air molecules, so the fewer the air molecules, the less would be the heat transfer. (Note for completeness: both clo measurements and windchill charts do not address radiative heat transfer, so the mass of air involved rules both calculations.)

So Dan, I think you are correct; that you have not seen an equation, because altitude/air pressure has been neglected in the relevant studies.

Rule of Thumb I was taught in my early days  –  Temperature changes 5.4°F/1,000 feet (9.8°C/1,000 meters) if it’s dry and 3.3°F/1,000 feet (6°C/1,000 meters) if it’s raining or snowing.