the.com/cold snap

means A sudden, brief spell of unusually sharp cold weather.

from A plain compound from 'cold' plus 'snap' — the same 'snap' as in a sudden crack or quick, abrupt action (as in a twig snapping, or a 'snap decision'). The word 'snap' itself goes back to a Germanic root for a sharp, quick noise or bite, related to Dutch and German words for snatching or snapping shut. Applied to weather, 'snap' captures how the cold arrives suddenly and briefly, like something clicking into place, rather than rolling in gradually — the phrase has been used this way since at least the 18th century.