Seoul's first snow: who has to see it, and where, for it to count?

The Korea Meteorological Administration records seasonal phenomena such as snow, frost, and ice based on a designated weather observatory in each region. For Seoul, that standard is the Seoul Weather Observatory in Songwol-dong, Jongno-gu, on the former site of the weather agency, and it sits 86 m above sea level.

Even if snow pours down at Gangnam Station, Seoul's first snow is not announced unless snowflakes are seen in Songwol-dong. Snow elsewhere is still noted, but it is left out of the official statistics, because only observations made at the same spot every year can be compared with past records.

The first snow is recorded not by a machine but by an observer who sees it. As of 2024, there are 23 observatories nationwide where people watch the sky directly, as in Seoul, and staff work in shifts to observe even at night.

The snow doesn't need to pile up, either. Even if it melts as soon as it falls, or comes as sleet mixed with rain, it counts as snow. That is why a brief flurry in the middle of the night can become the first snow, and some people only find out from the morning news.

People often think of the first snow and the first day snow piles up as the same record, but they are different. Snow depth is measured only once more than half of the observation field's ground is covered with snow.

The first ice also has a set method. An announcement that the first ice has formed in Seoul means that water in a metal observation container placed at the Songwol-dong observatory has frozen for the first time. A frozen puddle by the road does not immediately count as the first ice.

Seoul's normal first-snow date, averaged over 1991 to 2020, is November 20. But it varies a lot from year to year. In 2020 it didn't come until December 10, while in 2021 it came on November 10, ten days earlier than normal.

If you hear the first-snow news, look out the window, and see a clear sky, the Songwol-dong observatory may have caught a brief passing flurry. You can simply keep your own count of your neighborhood's first snow as the day you saw it yourself.