Korea has long used the phrase "samhansaon" for winter's pattern of a few cold days followed by a brief warm-up. Here's where the phrase comes from, whether it really follows an exact three-and-four-day cycle, and why it's used less often these days.
In winter, cold air keeps piling up over the Siberian continent, forming a powerful high-pressure system — the Siberian High. This high expands strongly to push cold air as far as the Korean peninsula, then weakens for a while before strengthening again. This cycle, where a cold snap arrives as the high strengthens and temperatures recover as it weakens, repeats roughly every few days — the origin of the phrase "samhansaon."
No. Samhansaon is simply an old figure of speech describing the Siberian High's rough strengthen-weaken cycle — it doesn't land on exactly three cold days and four warm ones every time. Some years the cycle stretches close to a week; other years it turns cold again after just two days. It's best understood as a traditional expression describing a general winter tendency rather than a precise schedule.
Recent analyses often point to changes in atmospheric circulation from global warming making the Siberian High's strengthen-weaken cycle less distinct than before. Instead, cold snaps arrive at unpredictable intervals, and unusually warm spells can appear even in the middle of winter. That said, the Siberian High itself hasn't disappeared, so periods of intense cold still occur.
Rather than assuming "it'll warm up soon" based on the samhansaon saying alone, it's safer to check each day's forecast. For general season-by-season tips, see the seasonal outdoor guide.
Since the samhansaon cycle isn't as regular as it used to be, saving the places you check often in sanCheck and checking the daily feels-like temperature and outdoor-activity score is a more effective way to prepare for winter cold snaps.