Highest temperature in Seoul on July 21?

Platform comparison

Market context

The market tracks the peak Celsius temperature at Incheon International Airport on 21 July 2026, a date falling within Seoul’s peak summer humidity. Historical data shows July highs typically reach 28°C, with a 43% daily rain probability and 80% relative humidity creating a thermally dense environment [1]. The current 0% YES crowd-implied probability suggests the market expects the temperature to fall outside the specific range offered, likely betting on a cooler day or a range mismatch rather than a literal impossibility of heat.

Programmatic traders should model this by scraping Wunderground’s daily history endpoint for RKSI to back-test July 21 extremes against the 2026 forecast. Comparable cases from recent years show July 21 temperatures often cluster near the 28°C average, but sudden convective rain can suppress peaks significantly [1]. A script monitoring the Korea Meteorological Administration’s hourly forecasts for the week prior would flag deviations; if the 7-day forecast predicts sustained cloud cover or precipitation, the 0% probability may hold, whereas a clear, high-pressure system would invalidate the current pricing.

Watch the mid-July forecast releases from the Korean meteorological authority, as these dictate the immediate thermal trajectory. Recent climate patterns indicate that humid, stagnant air masses in late July frequently push temperatures above 30°C, though rain events remain a critical variable [1]. Traders building conditional orders should tie execution to the 5-day forecast update; if the forecast shifts to a high-pressure ridge with minimal cloud cover, the 0% probability becomes a clear arbitrage opportunity against the historical 28°C baseline.

Sources: 1

Methodology

We track Highest temperature in Seoul on July 21? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Polymarket Review UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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 Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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.