Travel layering: one carry-on, four climates
Multi-climate trips defeat normal packing because each climate seems to demand its own wardrobe. The fix is a layer system where every piece works in at least two temperature bands. Here is the complete carry-on stack for a trip spanning 30F to 80F.
The principle
Never pack a single-climate piece. Every item must layer up or down: the tee that works alone at 80 also works under three layers at 40. If a piece only makes sense in one outfit or one temperature, it stays home.
The stack (12 pieces)
Base (3): two merino tees (odor resistance is the whole game on a travel rotation) and one merino long-sleeve. Mid (3): a fine crewneck knit, a button-down that works open as a light layer, and a packable insulated vest or thin puffer that compresses to nothing. Outer (2): an unlined trench or rain shell (the wind-and-rain layer that multiplies everything under it) and one structured jacket - blazer or chore coat - that doubles as the 'dressed' option. Bottoms (2): one tailored trouser, one dark jean. Shoes (2): leather sneakers worn on the plane, weatherproof boots or loafers in the bag.
The plane rule
Wear the heaviest layer stack in transit: boots, jeans, knit, structured jacket. It frees a third of the bag, and cabins run cold anyway. The trench packs flat on top.
The temperature map
80F: tee alone, sneakers. 65F: tee plus open button-down. 55F: long-sleeve plus knit. 45F: tee, knit, jacket. 35F and below: everything - base, knit, vest, jacket, trench over the top. The trench-as-outermost move is the one most people miss: a shell over insulation is how the same twelve pieces reach real winter.
Laundry math
Merino's odor resistance stretches the rotation: tees get three to four wears, the long-sleeve two, knits go the whole trip. A sink wash of socks and underwear at day four makes twelve pieces cover two weeks. The carry-on constraint stops being a constraint and becomes an edit.