Seoul Lowest Temp May 28: Will It Hit 18°C?

Seoul’s overnight low temperature on May 28 has become one of the sharper short-term weather markets on Polymarket right now. The 18°C outcome is trading at 73.5% implied probability, and the momentum behind that price is hard to ignore. A 39.5% surge in the YES price over the past 24 hours tells you this market moved fast on something, almost certainly a tightening weather forecast.

The market question asks: what will the lowest temperature in Seoul be on May 28? The 18°C outcome holds the YES at 0.74, the NO at 0.27. Resolution closes at 12:00 UTC on May 28, 2026. Total volume sits at $6,982, with $4,832 traded in the last 24 hours alone.

How the Seoul Temperature Contract Works

This contract resolves to YES if the official lowest temperature recorded in Seoul on May 28 equals 18°C, and NO if the low falls on any other listed value: 17°C, 16°C, 15°C, 19°C, 20°C, 21°C or higher, 14°C, 13°C, 12°C, or 11°C or below. The resolution source is the market’s stated resolution standard, tied to official meteorological observation for Seoul.

• YES (18°C lowest): trading at 0.74, implying a 73.5% probability that Seoul’s overnight low lands exactly at 18°C on May 28.
• NO (any other outcome): trading at 0.27, covering the full spread of alternative temperature outcomes listed above.

The NO side pays out if Seoul’s low drifts one degree warmer to 19°C or 20°C, or one degree cooler to 17°C or below. Late spring in Seoul sits in a volatile shoulder season. The Korea Meteorological Administration typically records overnight lows in the 14°C to 20°C range during late May, so the spread of competing outcomes is genuinely wide. A single-degree shift in boundary layer conditions overnight is enough to flip this market entirely.

Sponsored Partner

Momentum and Market Signals

The momentum composite here is unusually strong for a weather market of this size. The 1-hour price change of +30.0%, the 24-hour change of +39.5%, and a trend score of 76.57 all point in the same direction. The most plausible driver is an updated short-range forecast from a major numerical weather prediction model, likely the KMA’s own regional model or the ECMWF, narrowing the overnight low range squarely around 18°C for the Seoul metro area on the night of May 27 to 28.

Total volume of $6,982 is thin by prediction market standards. The $4,832 traded in the last 24 hours represents nearly 70% of all volume, which tells you this market woke up fast and late. Liquidity sits at $28,880, which is healthy relative to volume, but thin liquidity relative to a sharp price move means a single well-sized trade can push this price further in either direction before resolution. The market is pricing uncertainty, not science, and with this little volume, it is pricing it loosely.

• The 1-hour and 24-hour momentum composite is strongly bullish for the 18°C outcome, most likely driven by a converging numerical weather forecast for Seoul on May 28.
• Total volume of $6,982 flags this as a low-volume market. Price can move sharply on any new forecast data before the 12:00 UTC resolution window.
• Liquidity of $28,880 exceeds volume, which means the order book is not yet crowded. New capital entering either side would move the price noticeably.
• The 24-hour volume spike from a low base suggests a catalyst, almost certainly a forecast update, arrived within the last 24 hours.
• The YES price moved from 0.34 at open to 0.74 today, a near-doubling, which is an unusually sharp move for a single-day weather market this close to resolution.

Lines Analysis: Seoul’s Overnight Low and the Forecast Signal

The case for 18°C rests on whatever forecast convergence drove this price move. Seoul in late May sits at the transition between spring and early summer, when synoptic-scale systems can anchor overnight lows within a narrow band for 24 to 48 hours. If the dominant forecast model is consistently placing the morning low at 18°C, traders are right to price that with conviction. The Korea Meteorological Administration issues high-resolution localized forecasts for Seoul that tend to be reliable within a one-degree margin at this range. Here’s what the measurements are telling us: the overnight temperature gradient in Seoul during late May is shallow, meaning the difference between an 18°C and 17°C or 19°C low depends on cloud cover, wind shift timing, and urban heat retention, all factors that become more predictable at short range.

The competing outcomes are real. A warmer-than-expected evening, persistent cloud cover trapping heat, or a weaker-than-forecast cold advection could push the low to 19°C or 20°C. Conversely, a clearer sky, a dry northwesterly flow, or earlier-than-expected cooling could drop the low to 17°C. The NO side at 0.27 captures every one of those alternatives. Given the thin volume, it only takes one updated model run showing a 19°C low to pull capital toward NO quickly before the 12:00 UTC close.

• A KMA forecast update placing the overnight low at 19°C or higher would pressure the YES price sharply lower before resolution.
• Confirmation from the ECMWF or GFS model suite anchoring the low at 18°C through the overnight hours on May 28 would reinforce the current market price.
• Cloud cover and urban heat retention data for the Seoul metro area on the evening of May 27 is the most direct leading indicator to monitor.
• Any wind shift toward a northwesterly flow over the Korean Peninsula overnight increases the probability of a sub-18°C low.
• The 12:00 UTC resolution window means the decisive temperature reading will likely be the early morning minimum, typically recorded between 03:00 and 06:00 local Seoul time.

Total volume of $6,982 is thin enough that this market should be read as a sentiment signal, not a deeply researched consensus. The data doesn’t care about the politics, and in a market this small, it barely cares about the traders either. The directional lean is clearly toward 18°C, but with this little capital behind it, that lean reflects a forecast input more than sustained conviction.

LINES VERDICT

FORECAST-DRIVEN LEAN TOWARD EIGHTEEN DEGREES

The price surge in the last 24 hours points to a converging short-range forecast placing Seoul’s May 28 overnight low at exactly 18°C. The market is pricing that forecast signal, not a guaranteed outcome.

What the market says: The 18°C outcome carries a 73.5% implied probability as of May 27, 2026. That reflects strong short-term forecast convergence, but thin volume means this price is fragile and will reprice quickly on any new model run before the 12:00 UTC resolution close on May 28.

Key unknown: The single most important input is the next KMA or ECMWF short-range forecast update for Seoul overnight on May 27 to 28. Any shift of one degree in the projected morning minimum would materially reprice every outcome in this contract.

Scientific Context: Seoul Late May Temperature Climatology

Seoul’s late May overnight lows historically range from the mid-teens to the low twenties Celsius, with the climatological mean minimum for the final week of May sitting near 16°C to 18°C based on Korea Meteorological Administration historical records. Urban heat island effects in the Seoul metro area tend to keep overnight lows one to two degrees warmer than rural surroundings. The 18°C target sits squarely within the climatological normal range for this period. That context supports the market’s current lean, but it also means the adjacent outcomes at 17°C and 19°C are statistically plausible and should not be dismissed. Events that would move this price before the May 28 resolution include any KMA advisory, a significant shift in the synoptic pattern over the Korean Peninsula, or late-evening cloud cover changes affecting radiative cooling rates overnight.

How likely is an 18°C lowest temperature in Seoul on May 28?

The market prices it at 73.5% as of May 27, 2026, reflecting a converging short-range forecast. That number means roughly a one-in-four chance the low lands somewhere else.

What does the NO contract cover?

The NO outcome at 0.27 covers every listed alternative: 17°C, 16°C, 15°C, 14°C, 13°C, 12°C, 11°C or below, 19°C, 20°C, and 21°C or higher. Any of those outcomes pays out the NO position.

What data event would most move this price?

A new KMA or ECMWF forecast run placing Seoul’s overnight low outside the 18°C range would shift capital fast. This market is forecast-sensitive and resolves within hours.

When does this market resolve?

Resolution closes at 12:00 UTC on May 28, 2026, timed to capture the official overnight minimum temperature recording for Seoul.

Is the volume reliable for this market?

Total volume of $6,982 is low. The $28,880 in liquidity exceeds volume, which means the price can move sharply on a small number of new trades before the resolution window closes.