The question of whether ice is colder than snow blends physics with human perception. Although ice often feels colder to the touch than snow, a direct temperature reading usually reveals a different reality. Both ice and snow are forms of frozen water, chemically identical, and their actual temperature is governed by the environment around them.
Temperature and Thermal Equilibrium
Temperature is an intrinsic measurement of the internal thermal energy of a substance. When ice and snow exist in the same environment, they tend toward a state of thermal equilibrium with the surrounding air. If the ambient temperature is below the freezing point of water, both substances will eventually settle at the same temperature as the air and each other.
The temperature of any stable ice or snow mass that is not actively melting is at or below 0° Celsius (32° Fahrenheit). If snow and a block of ice are placed side-by-side on a sub-freezing surface, a thermometer would register them as having virtually the same temperature. The feeling of “colder” is a subjective experience related to the speed at which heat is pulled away from the skin, not the substance’s actual temperature.
Structural Differences Between Ice and Snow
The reason for the difference in how ice and snow feel lies in their physical structures. Ice is formed by the freezing of liquid water, resulting in a dense, solid, and compacted crystalline lattice. The density of ice is approximately 917 kilograms per cubic meter (kg/m³) at 0°C, a structure containing very little trapped air.
Snow is a collection of individual ice crystals that form directly from water vapor in the atmosphere. This structure is highly porous, trapping a significant volume of air within and between the flakes. Freshly fallen snow can contain as much as 90% air, with densities often ranging from 50 to 70 kg/m³. This high air content is the defining physical contrast between the two forms of frozen water.
Thermal Conductivity and Insulation
The difference in air content directly influences the thermal conductivity of each material, which is its ability to transfer heat. Ice is a relatively good conductor of heat, with a thermal conductivity coefficient around 2.2 Watts per meter-Kelvin (W/m·K) at 0°C. When skin touches a dense block of ice, heat from the body is rapidly transferred into the ice, creating the immediate and sharp sensation of intense cold.
The air trapped in the intricate structure of snow is a poor conductor of heat, as still air has a very low thermal conductivity of about 0.022 W/m·K. This makes snow an excellent thermal insulator, dramatically slowing the transfer of heat away from an object or body. The thermal conductivity of snow is much lower than ice, typically ranging from 0.04 to 0.4 W/m·K, depending on its density. This explains why animals can burrow into a snowpack for warmth, as the snow acts as a protective blanket, preventing heat loss to the frigid air above.