Highest temperature in Seoul (Incheon) on August 20?

Platform comparison

Market context

Seoul's peak temperature on 20 August 2026 will be measured at Incheon International Airport Station and resolved against Weather Underground's Daily Observations table. The crowd currently assigns zero probability to any outcome occurring, suggesting either a technical issue with market setup or genuine uncertainty about whether conditions will fall within the specified range. August in Seoul typically sees daily highs between 28–32°C, with extreme heat events pushing above 35°C becoming more frequent due to longer-term warming trends across East Asia.

Historical August data from Incheon shows that temperatures exceeding 33°C occur roughly once every two to three years during the month, whilst readings above 35°C remain relatively rare but have been recorded in four of the past fifteen years. The 2018 heatwave saw Seoul reach 39.6°C, and 2022 brought sustained temperatures above 34°C for extended periods. These precedents suggest the market's 0% reading undervalues the likelihood of moderate-to-high outcomes, particularly given that late August typically remains warmer than early-month readings.

Traders should monitor the East Asian summer monsoon pattern and any developing high-pressure systems across the Korean Peninsula in the weeks preceding 20 August. The Korea Meteorological Administration publishes extended forecasts approximately two weeks ahead, which will provide clarity on whether atmospheric conditions favour heat accumulation or cooler maritime influence. Typhoon activity during August can dramatically suppress temperatures, making seasonal storm tracks a critical variable for resolution outcomes.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

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.

UK Frequently Asked Questions

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 Who Will Win. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.