Highest temperature in Seoul on May 21?

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Market context

Incheon International Airport’s recorded high for 21 May will settle this market, with the final figure taken from Weather Underground’s daily history once the day is complete. At midday UTC, the market is pricing a 0% yes outcome, which usually reflects either a very low temperature band already implied by the forecast or a lack of trading interest rather than a literal impossibility. Because resolution depends on the airport station’s maximum for the full local day, late-afternoon warming in Korea still matters more than the morning reading.

For context, Seoul and the capital area have already seen unusually warm conditions this May. Chosun reported that Seoul set its hottest May temperature on 21 May 2025, with inland districts above 30°C, and the heat was expected to persist into the following day. That does not directly determine Incheon airport’s reading, but it frames how quickly late-spring temperatures can overshoot seasonal norms in north-western Korea. By comparison, long-run climate data for Seoul show May highs typically rising through the month and often landing in the high teens to mid-20s Celsius, so a settlement in a modest band would be more consistent with climatology than a one-off heat spike.

The main catalysts are the Korea Meteorological Administration’s short- and medium-range forecasts and any afternoon cloud or maritime-breeze effects near Incheon, which can cap the airport’s maximum even when inland Seoul runs warmer. Traders should also watch whether the temperature peak occurs before or after local afternoon heating, since the contract settles on the day’s highest observation rather than the daily average. On-chain, the market settles in USDC, so the only material crypto link is liquidity: spot BTC and ETH swings, or broader risk-off moves, can affect how much capital sits in the book, but they do not affect the weather outcome.

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Methodology

Methodologically this overview focuses on on-chain pricing: Polymarket's live mid comes from the Polygon conditional-token order book and settles automatically in USDC. The other three venues — Kalshi, Betfair, Manifold — are listed with their platform attributes, because they operate off-chain and a 1:1 comparison of contract mechanics isn't possible.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

FAQ

Is this market available outside the US?

PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does it cost to trade on PolyGram?

Zero. PolyGram routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, PolyGram triggers a quick verification flow that finishes in minutes.