Highest temperature in Seoul on May 21?

Platform comparison

Active sub-markets

Market context

Seoul is already running hot for mid-May, but the contract is really about the reading at Incheon International Airport, where sea-breeze effects often keep the top end a few degrees below central Seoul. With the market showing 0% YES, the favourite is clearly the cooler bands: anything in the low-to-mid 20s C looks like consensus, while the contrarian value sits on a brief late-day push into the upper 20s if sunshine persists and the marine layer stays weak. The key handicap is that the airport’s microclimate can lag the city core, so a Seoul heat headline does not automatically translate into the highest airport temperature clearing the hottest brackets.

The closest guide is the run of very warm weather across the capital earlier this week. Korean media reported Seoul’s lowest temperature reached 23C on 21 May, the warmest May morning on record, and daytime readings climbed above 30C in several districts, with officials saying the heat would continue until the 22nd before easing from the 23rd. That supports a bullish case for the upper bands if the warm air mass holds, but it also frames the underdog angle: the KMA has already signalled cooling after the 22nd, and Incheon’s airport station is exposed to onshore flow, which can cap the daily maximum even when inland Seoul runs well above seasonal norms.

Traders should watch the Korea Meteorological Administration’s short-range updates, cloud cover, and wind direction through the afternoon, because a shift to a stronger sea breeze would pull the settlement reading towards the lower favourites. The practical dependency is timing: the market resolves on the final daily maximum from Wunderground for RKSI, so the high can be set by a short early-afternoon spike and then stand even if temperatures ease later. Recent reporting from Chosun and Korea JoongAng Daily shows the broader region has just posted record May warmth, but for this market the deciding factor is whether that warmth reaches the airport station before coastal moderation kicks in.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in Seoul on May 21? across five venues. We show live odds for Polymarket-based markets (sourced from the Polygon order book); for other venues we list platform attributes, since the comparable contracts are not exposed via a public API on every venue. Every CTA points at PolyGram — the application we operate, where you trade directly against the Polymarket order book at 0% fees.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 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 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.

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.