Highest temperature in Seoul on May 21?

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Market context

Seoul’s air on 21 May will be judged by the highest reading at Incheon Intl Airport Station, and Polymarket is marking that outcome at 0% YES in USDC on Polygon, via conditional tokens. That pricing implies the contract is being treated as effectively settled unless a late-day spike is still possible before the settlement window closes at 12:00 UTC. With the market resolving to a Celsius range from the final Wunderground daily high, the key point is whether the airport station gets anywhere near a materially warmer band than the market has already discounted.

For context, late May in the Seoul area is usually mild to warm rather than hot. Typical Seoul highs are around 21–27°C, with WeatherSpark showing an average rise through the month from about 20°C to 25°C, and lows still cool enough to keep the daily range moderate. Comparable late-May readings at Incheon often sit in the low-to-mid 20s Celsius unless there is an unusually warm air mass. Recent history also suggests upside is limited: Incheon’s recent daily extremes on Wunderground have not shown a pattern of frequent 30°C-plus highs this far into spring, which helps explain why the market is anchored so low.

The main catalyst is the day’s actual weather at and around Incheon rather than any scheduled event. Traders should watch KMA short-range forecasts, cloud cover, onshore breeze changes, and whether a warm sector reaches north-western Seoul by early afternoon. Rain or marine flow would cap the high; bright sun and a stronger southerly push could lift the reading, but only if conditions improve before the midday settlement cut-off. For Polymarket users, the practical issue is whether the final Wunderground station maximum can still move into a higher range before the market closes to new information.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote (Polymarket), four reference venues with their key attributes, and a single execution path — every trade button routes to PolyGram, which mirrors the Polymarket order book directly.

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 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.

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 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.