Weather, past and ahead.

The Gagge two-node model estimates skin/core heat balance and skin wettedness for every hour and outfit. It uses air temperature, humidity, estimated mean radiant temperature, local air speed, activity and clothing resistance. Apparent temperature stays a weather summary; it is not fed into this calculation.

A shell reduces wind penetration through the assembled outfit and preserves insulation underneath. Wind still cools its outer surface and exposed areas. The shell also restricts evaporation; its benefit is not a fixed temperature bonus.

These garment properties are editable starting estimates. They are not measurements of your garments. Trousers, underwear, socks and shoes are held fixed. Lower air permeability means less wind penetration; lower vapour efficiency means less evaporation. Equal initial midlayer insulation avoids assuming a universal warmth ranking.

Thermal sensation: −3 cold, −2 cool, −1 slightly cool, 0 neutral, +1 slightly warm, +2 warm, +3 hot. Default acceptable range: −0.5 to +0.5. “Usually cold/hot” shifts predicted sensation by −0.5/+0.5. Activity uses 1.2, 2 or 3 met.

The optimizer finds the lowest total discomfort among all permitted outfits and schedules: no more than three adjustment occasions, including shell changes. Outfits can change at any hourly boundary, so a period can last just one hour; there is no extra minimum-duration rule. A swap of two garments at the same time is one occasion. Rain requires a shell outdoors; the optimizer can put it on early or keep it on longer to stay within the change budget. Missing weather leaves comfort unassessed and is flagged.

Each hourly calculation starts from the model’s neutral state and simulates about an hour. This is a comfort comparison, not a continuous physiological or cold/heat safety prediction. Sun/shade and wind shelter, permeability, fit compression, moisture resistance and clothing coverage use documented approximations. Solar input is the preceding-hour horizontal shortwave average, not a direct measurement of your exposure. Nighttime and shade assume radiant temperature equals air temperature.

Method references: Gagge two-node model · ASHRAE thermal comfort · Thermal model license. Full equations and limitations are included in the source download.