The cores of vortices spin at very high speed and are regions of very low pressure. To first approximation, these low-pressure regions form with little exchange of heat with the neighboring regions (i.e., adiabatically), so the local temperature in the low-pressure regions drops, too.[6] If it drops below the local dew point, there results a condensation of water vapor present in the cores of wingtip vortices, making them visible.[6] The temperature may even drop below the local freezing point, in which case ice crystals will form inside the cores.[6]