A colour with a red, orange or yellow bias — associated with heat, sunlight and cosiness.
In Colourwise's classification, a colour whose OKLCH hue falls roughly between 20° and 95°.
Warm/cool is a design convention, not a measured physical property of light temperature.
Terracotta and mustard are warm colours.
Warm colours are commonly recommended for north-facing rooms to counteract cool daylight.