Supercooled Water Water normally freezes at 273.15 K (0 °C or 32 °F) however it can also be "supercooled" at standard pressure down to its crystal homogeneous nucleation at almost 224.8 K (−48.3 °C/−55 °F). The process of supercooling requires that water be pure and free of nucleation sites, but the cooling itself does not require any specialized technique. At this state, it will remain liquid until it is disturbed. When it is agitated, the liquid 'freezes' and crystalizes to form ice. It may seem counter intuitive, but in the image the supercooled water is actually incurring an exothermic reaction — the liquid itself is rapidly warming to form ice.