Highest temperature in Seoul on May 31?

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Market context

On 31 May 2026, the highest temperature recorded at Incheon International Airport Station will determine the resolution of this market. Seoul's late May weather typically sits in the warm-to-hot range, with historical daily highs averaging 26–28°C during this period. The settlement will draw from Wunderground's historical weather database, which logs hourly readings throughout the day to establish the peak temperature.

Seoul experiences late spring conditions by the end of May, transitioning toward the humid subtropical summer pattern that dominates June onwards. Over the past decade, 31 May highs at Incheon have ranged from 22°C in cooler years to 32°C during warmer spells, with most occurrences clustering between 25–29°C. The 0% crowd probability suggests traders are either uncertain about the specific temperature bands offered or treating this as a calibration exercise rather than a genuine forecast. Comparable late-May days show considerable year-to-year variability driven by whether high-pressure systems or frontal systems dominate the Korean peninsula.

The key variable affecting 31 May 2026 will be the large-scale atmospheric pattern established in late May—specifically whether a Tibetan high-pressure system pushes northeastward into the region or whether a frontal boundary stalls nearby. South Korea's meteorological service typically issues extended forecasts by mid-May that would clarify whether anomalous warmth or cooler conditions are expected. Traders should monitor the Korea Meteorological Administration's 10-day outlooks released in the final week of May, as these provide the most reliable guidance for temperature ranges at that lead time.

Methodology

We track Highest temperature in Seoul on May 31? on the five venues with material liquidity for prediction markets. Live odds come from the Polymarket Polygon order book — the only source that ships real-time data under an open licence. For Kalshi, Betfair and Manifold we list platform attributes (fee, KYC, settlement, payment) instead of fabricated odds, because their APIs use non-comparable contract definitions.

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?

On Sport Prediction, which mirrors the Polymarket order book at 0% fees. 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.

What does it cost to trade on Sport Prediction?

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

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?

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