Highest temperature in Seoul on May 21?

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Active sub-markets

Market context

Seoul is in a warm, late-spring phase, but not a uniformly hot one. Typical May daytime highs in the city rise through the month from the high teens Celsius to around 25°C, with recent climatology putting the average high near 21°C and the average low near 14°C. That makes a maximum temperature in the low-to-mid 20s the most common outcome, while readings close to 30°C are possible but materially less frequent. For a single-day market with a zero per cent crowd price, the relevant comparison is not the monthly mean but the tail: whether that day gets one of the brighter, sunnier breaks that can briefly push temperatures above forecast norms.

The main catalysts are local sunshine, wind direction, and any passing showers or cloud bands over the Seoul–Incheon corridor. Wunderground’s historical Seoul data show May has produced highs well into the upper 20s Celsius, but it has also delivered cool outliers in the low teens, underlining how sensitive the daily maximum is to cloud cover and rain timing. WeatherSpark’s May climatology for Seoul also points to only moderate cloudiness overall, so the day’s peak can move quickly if skies clear by late morning. With settlement based on the Incheon Intl Airport Station reading for 21 May, traders should watch the final morning forecast, any short-range KMA updates, and whether precipitation arrives early enough to cap the day’s maximum before afternoon heating can build.

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Methodology

We track Highest temperature in Seoul on May 21? 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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

FAQ

Where can I trade this market with the lowest fees?

On PolyGram, 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.

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 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, PolyGram 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.