A cold snap is a short, sharp period of unusually cold weather that follows a milder period. It serves as a quick reminder of the approaching winter. In late fall, it can cause sudden frosts, frozen puddles, or even early flurries. These brief chill surges occur when Arctic air pushes southward behind a passing front. Although temporary, they can shock unprepared plants, pipes, and people, prompting them to take out their coats earlier than expected.