Highest temperature in Tokyo on August 21?

Platform comparison

Market context

Tokyo will experience peak summer heat on 21 August 2026, with the highest temperature recorded at Haneda Airport Station determining settlement. The market currently prices this contract at 0% YES across all temperature ranges, reflecting the settlement window's distance and inherent uncertainty in long-range weather forecasting. Traders are pricing in the difficulty of predicting specific temperature bands nearly two years forward, though historical August data from Tokyo provides a baseline for calibration.

August temperatures at Tokyo Haneda have historically ranged between 28–35°C, with peaks typically occurring in mid-to-late afternoon hours. The Japan Meteorological Agency's records show that extreme heat events—temperatures exceeding 36°C—occur roughly once every three to five years during August in the Kanto region. The 0% pricing suggests the market is treating all temperature outcomes as genuinely uncertain rather than favouring any particular range, a rational stance given the 24-month forecast horizon and the inherent variability of seasonal weather patterns.

Traders monitoring this contract should track updates from the Japan Meteorological Agency's seasonal forecasts, typically released in June and July 2026, which may shift probability distributions as the settlement date approaches. El Niño or La Niña conditions developing in the Pacific will influence broader temperature trends across East Asia. The resolution mechanism's specificity—requiring data from Weather Underground's Daily Observations table rather than summary figures—means traders should familiarise themselves with Haneda's historical reporting patterns to understand potential discrepancies between sources that might affect settlement interpretation.

Methodology

We track Highest temperature in Tokyo on August 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

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.

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 Polymarket Alternative 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.

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%.