Highest temperature in Seoul on July 21?

Platform comparison

Market context

Seoul’s Incheon International Airport will record its peak temperature for 21 July 2026, with the outcome settled via Wunderground’s daily history for the RKSI station. The prediction market currently shows a 0% implied probability for any “YES” outcome on a specific unlisted threshold, while Polymarket’s parallel contract on the same event assigns an 86% chance to 27°C as the frontrunner, with 28°C at 10% [1]. This stark divergence between a zero-probability line on one platform and a high-confidence 27°C consensus on another highlights inconsistent pricing across cross-platform odds for the same weather event.

Historical July peaks at Incheon typically cluster between 26°C and 31°C, with 27°C appearing frequently in recent decades as a median high rather than an outlier. The 86% weighting on 27°C in the Polymarket contract aligns with this pattern, suggesting traders view it as the most probable band, whereas the 0% line elsewhere may reflect a mispriced binary question or a threshold set above likely outcomes [1]. Such gaps often emerge when platforms frame the same event with different resolution conditions, creating arbitrage opportunities for those comparing implied probabilities.

Traders should monitor Korea Meteorological Administration forecasts for the week leading into 21 July, particularly any updates on monsoon intensity or heat-advisory announcements, as these directly influence peak temperatures. Wunderground’s daily RKSI record will be the sole resolution source, so any data gaps or station anomalies could delay settlement, though no such issues are currently reported. With settlement closing at 12:00 UTC on 21 July 2026, the window for adjusting positions based on evolving weather models remains narrow but actionable.

Sources: 1

Methodology

We track Highest temperature in Seoul on July 21? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Best Prediction Markets UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Best Prediction Markets UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.