Highest temperature in Tokyo on August 21?

Platform comparison

Market context

Tokyo's highest temperature on 21 August 2026 will be measured at Haneda Airport Station and recorded in Weather Underground's Daily Observations table, with the contract settling to whichever temperature band contains that peak reading in degrees Celsius. The current 0% YES probability reflects the market's pricing of this specific outcome across available ranges, with USDC settlement on Polygon conditional tokens determining payouts once the settlement window closes on 21 August at 12:00 UTC.

Historical August temperatures at Tokyo Haneda show consistent patterns useful for calibrating expectations. The airport typically records highs between 32–35°C during mid-August, with occasional excursions toward 36–37°C during heat waves. August 2023 saw a peak of 35.1°C on the 21st itself, whilst August 2022 reached 36.1°C on the same date. These precedents suggest the market's current pricing may be anchoring to specific temperature bands rather than treating all outcomes as equally probable; traders should examine which ranges carry the heaviest liquidity to understand where consensus sits.

Japan's Meteorological Agency issues seasonal outlooks in early August that influence temperature forecasts for the month's latter half. El Niño or La Niña conditions, tracked through NOAA updates, materially affect Pacific heat patterns reaching Tokyo. Traders monitoring late July and early August weather models—particularly from JMA and international centres—will gain early signals about whether 21 August conditions favour cooler or warmer extremes. Urban heat island effects around Haneda, intensified during sustained high-pressure systems, remain a key variable distinguishing airport readings from broader Tokyo measurements.

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

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 PolyGram. 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%.