In a carrier your own warmth counts as a layer, so the app dresses a carried baby one layer lighter than a baby in a pram, and in the cold puts a blanket or your own coat over the carrier rather than a bulky jacket on the baby.
What the app suggests in a carrier, from the skin out, for a baby of 6–12 months:
20°C: short-sleeve bodysuit, pants and socks. Warm — light single layers. 16–19°C: long-sleeve bodysuit, pants and socks. Mild — add a light mid layer. Carried close, your warmth counts — one layer less. 15°C: long-sleeve bodysuit, pants, socks and light sweater. Mild — add a light mid layer. 13–14°C: long-sleeve bodysuit, pants, socks, light sweater and warm hat. Mild — add a light mid layer. 12°C: long-sleeve bodysuit, warm pants, socks, light sweater and warm hat. Cool — a mid layer plus a hat. 11°C: long-sleeve bodysuit, warm pants, warm socks, light sweater and warm hat. Cool — a mid layer plus a hat. 7–10°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater and warm hat. Cool — a mid layer plus a hat. 6°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater, warm hat and blanket over the carrier. Cold — full outer layer and a hat. Carried close — a blanket over the carrier beats a bulky jacket. 1–5°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater, warm hat, mittens and blanket over the carrier. Cold — full outer layer and a hat. Carried close — a blanket over the carrier beats a bulky jacket. −15 – 0°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater, warm hat, warm mittens and blanket over the carrier. Freezing — everything on, cover the hands. Carried close — a blanket over the carrier beats a bulky jacket.
Held close against you, your baby shares your body heat. A snowsuit inside a carrier usually ends in a hot, sweaty baby by the time you are indoors.
On a dry day below 14°C, the app puts a blanket over the carrier instead of the jacket. Hat and mittens stay on, since the head, hands and feet stick out.
Check the neck once you have been walking a while: warm but not sweaty is just right.
0–3 months, 5°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater, warm hat, mittens and blanket over the carrier. 3–6 months, 5°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater, warm hat, mittens and blanket over the carrier. 6–12 months, 5°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater, warm hat, mittens and blanket over the carrier. 1–3 years, 5°C: long-sleeve bodysuit, warm pants, warm socks, warm sweater, warm hat and blanket over the carrier.
Indoors, or in a warm car, bus or train, take the hat and outer layers off.
Check the neck — warm but not sweaty means just right.