Here in California the conditions on a spring day can have an apparent temperature swing of 100F. I'm talking potential frostbite to heat stroke back to frostbite in 8 hours. At high altitudes, extreme solar radiation will bake and burn you, then when the sun goes down the temperature will drop 50 degrees in an hour. I finally seemed to have a system mostly dialed for a climb of Whitney last spring, where temps ranged from cool at the parking lot, to an apparent temperature (calm, intense solar radiation reflected off spring snow) of 80+, to single digits and windy on the summit. With an unlimited budget I would tweak this setup but not make major changes to the basic layering theme.
From the skin out- Top:
-Merino or Merino/Viscose blend T-shirt (about 200 gsm fabric)
-Railriders Regulator Wind Shirt. This shirt is 3 osy nylon which is wind resistant but breathes quite well- not nearly as wind resistant as a Houdini. It has zippered mesh side vents wrist to waist and high sun collar. Tan color. I sewed the rear yoke vent closed.
-Thin Merino Beanie. Keeps the sweat out of my eyes.
-Sun hat or climbing helmet.
-Lightly insulated leather gloves.
-Schoeller Dynamic pants (tough, stretchy, wind-resistant but breathe very well) (I wish they had thigh vents and were not black)
-Long Johns- none to either light 3 oz or heavy 6 oz grid Polartech PowerDry depending on what I expect conditions to be.
These first layers work well climbing up in calm to breezy conditions with extreme solar radiation. Say freezing/calm to 60F during exertion.
Cooler but still moving add:
-Fleece hoodie with thumbloops. If I expect it to be cold all day sometimes I put this under the Regulator shirt or leave the Regulator off. (Would like a Pat. R1 Hoodie but mine was only $25)
-Again, depending on expected temp I may add a long sleeve merino shirt or merino sweater vest ($5 at thrift store, Santorum style)
-Patagonia Houdini wind shirt if I'm sure there's no chance of liquid precipitation. Otherwise a Marmot Precip jacket.
At rest/backup warmth/extreme conditions:
-Puffy down jacket. (New Balance Fugu) I would rather have a hood.
-Lowe Alpine "Magma" Primaloft full-zip pants. Go right over the other pants without taking off boots.
-Thick fleece lined, shell outer "bomber hat". (Would prefer a good hood on the down jacket)
-Thick over-mittens, thin liner gloves.
-Windproof face mask & goggles.
Yes, there's some redundancy in this setup but the two wind-shirts are worth it in my mind. I have never found a puffy jacket to be comfortable on the move so I go with merino, fleece, and separate wind layers.