Highest temperature in Seoul on June 20?

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Market context

The key real-world driver is the **highest temperature recorded at Incheon International Airport** on 20 June 2026, not a citywide average, so late-day heating, cloud cover and sea-breeze effects matter more than broad Seoul impressions. WeatherSpark’s June climatology for Seoul puts average daily highs around **77°F to 81°F** (about **25°C to 27°C**), with readings rarely falling below **68°F** or exceeding **87°F**[2]. That makes a **24°C** outcome look broadly consistent with seasonal norms, while a materially hotter reading would need an above-average warm spell or unusually strong sunshine. Polymarket’s current book is much more aggressive than the crowd-implied **1% YES** on the contract framing, with **24°C** shown as the clear frontrunner at **84%** on the related outcome market[1].

For comparison, recent Korean heat records show that extreme June warmth is possible, but the upper tail is still uncommon. Weather Underground notes South Korea’s all-time national heat record is **41.0°C** at Hongcheon, and the Korea Times reported Seoul’s highest June temperature record at **29.4°C** set on **20 June last year**[3][6]. That historical context supports a market concentrated around the mid-20s Celsius rather than the high-20s or low-30s, which helps explain why traders may treat anything above **25°C** as a lower-probability tail rather than the base case. The present contract’s **1% YES** also suggests either a mismatch in contract definition or a very different threshold structure from the main temperature bucket market.

The main catalysts are the day’s actual airport observations and any late changes in the surface pattern over the Seoul metropolitan area, especially cloud breaks, rainfall timing and wind direction. At **4:00 UTC**, the market is still open to the full diurnal range, so the settlement reading can move sharply if afternoon heating accelerates. Traders should also watch for any differences between city forecasts and the official **Incheon Intl Airport Station** reading, since airport exposure to marine influence can keep the maximum below downtown Seoul expectations. No additional announcement is required; the decisive inputs are the live weather evolution and the eventual Wunderground daily history entry used for settlement[2].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Seoul on June 20? 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 Best Prediction Markets, 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.

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 Best Prediction Markets?

Zero. Best Prediction Markets 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, Best Prediction Markets triggers a quick verification flow that finishes in minutes.

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.