As Newton's law of cooling states, the rate of cooling of an object – whether by conduction, convection, or radiation – is approximately proportional to the temperature difference Δ T. Frozen food will warm up faster in a warm room than in a cold room. Note that the rate of cooling experienced on a cold day can be increased by the added convection effect of the wind. This is referred to as wind chill. For example, a wind chill of -20 °C means that heat is being lost at the same rate as if the temperature were -20 °C without wind.