Seoul in mid-May typically experiences daytime highs ranging from 20 to 27°C, depending on synoptic weather patterns and frontal systems moving across the Korean Peninsula. A daily high temperature of exactly 21°C represents a relatively cool outcome for Seoul at this time of year, when spring warming pushes toward early summer conditions. The market prices this precise outcome at just 1% YES, reflecting strong trader conviction that Seoul's May 18 high will exceed 21°C. The resolving criteria are unambiguous: the highest temperature (in whole degrees Celsius) recorded in Seoul on May 18, 2026, compared against the exact 21°C threshold. This type of granular weather market attracts both amateur weather enthusiasts and professional meteorological traders testing forecast accuracy and climate patterns. The 1% odds imply traders collectively expect Seoul to be warmer—either a clear sunny day with robust insolation or an unseasonably warm pressure pattern for mid-May. Historical Seoul May weather and current seasonal anomalies likely inform this pricing. The 24-hour volume of $2,939 indicates moderate trader engagement despite the low YES odds and short two-day time horizon.
What factors could move this market?
Seoul's climate in mid-May sits at a natural inflection point between late spring and early summer. Historically, May 18 highs in Seoul range from 18°C to 29°C across four decades of meteorological records. The Korean Peninsula experiences increasingly volatile weather during May due to competing air masses: the remnants of cooler continental polar air from Mongolia and Siberia clash with warm tropical maritime air advancing northward from the Pacific. The exact temperature threshold of 21°C is remarkably narrow and requires a specific weather regime to materialize.
Factors pushing the outcome toward YES are limited but plausible. A weak upper-level low-pressure system stalled over Korea, combined with persistent cloud cover and cool northerly winds, could suppress the daily high to only 21°C. Recent May patterns from 2019 and 2020 show occasional days where Seoul recorded highs near 20–22°C despite being late spring. A delayed warm surge or a mid-latitude cyclone moving through could prevent typical May heating. Such days are notable but historically uncommon by mid-May.
Factors pushing toward NO (higher temperatures) dominate seasonal climatology. Seoul's average high in mid-May is approximately 24°C, with typical maximums clustering around 24–26°C. Recent climate trends show spring warming accelerating—Seoul's May temperatures have drifted warmer over the past two decades. A high-pressure ridge positioned over Korea, clear skies, and southerly winds could easily push the high to 26–28°C. The current 1% YES odds reflect this overwhelming statistical improbability: hitting exactly 21°C is an outlier requiring coolness that May rarely delivers to Seoul.
Analogous low-probability weather markets in past years reveal trader behavior: outcomes priced below 2% typically occur in fewer than 1% of resolved cases. Seoul's seasonal pattern strongly disfavors this threshold. The 1% pricing also reflects the short two-day window—no material new meteorological forecasts will likely shift the consensus that Seoul will be warmer. The $7,602 total liquidity shows this market remains relatively illiquid, typical for hyper-specific weather contracts. Traders pricing YES at 1% are essentially betting on a surprise cool snap.
What are traders watching for?
Upper-level atmospheric pressure patterns and cloud cover forecast for Seoul on May 18 will determine whether daytime heating reaches typical spring levels.
Cool northerly wind direction and any lingering cold air masses from Mongolia or Siberia advancing over Korea before May 18 could suppress daytime highs.
Recent meteorological model consensus (GFS, ECMWF, KMA) released 1-2 days before May 18 will likely solidify trader conviction around the final outcome.
Seoul's actual recorded high temperature on May 18 reported by Korea Meteorological Administration by end of day will be the official resolution criteria.
How does this market resolve?
The market resolves YES if Seoul's highest recorded temperature on May 18, 2026 equals exactly 21°C (whole degrees Celsius) as reported by the Korea Meteorological Administration. It resolves NO if the high is any temperature other than 21°C.
Polymarket Trade is an independent third-party interface to the Polymarket CLOB prediction market exchange on Polygon — not affiliated with Polymarket, Inc. Prediction markets aggregate trader expectations into real-time probability estimates. Every market question resolves YES or NO based on a specific event outcome; traders buy shares of the side they believe will resolve positively. Prices range 0¢ (certain no) to 100¢ (certain yes) and naturally reflect the crowd-implied probability of YES. Polymarket Trade is non-custodial — your funds never leave your wallet. Open the full interactive page linked above to place orders, see order book depth, and execute a trade.
