Highest temperature in Tokyo on August 18?

Platform comparison

Market context

Tokyo's weather on 18 August 2026 will be shaped by the tail end of Japan's summer monsoon season, when the city typically experiences its most intense heat. August historically ranks as Tokyo's hottest month, with daily maxima regularly exceeding 35°C at Haneda Airport. The 0% crowd probability suggests traders are pricing in either extreme confidence in a specific temperature band or uncertainty about which range will ultimately contain the day's peak reading.

Historical August data from Haneda shows considerable year-to-year variation. The station recorded 37.2°C on 16 August 2023 and 36.4°C on 10 August 2024, whilst cooler Augusts have seen peaks in the 32–34°C range. The resolution methodology—drawing from Weather Underground's Daily Observations table rather than summary figures—introduces a technical dependency that occasionally produces discrepancies from other meteorological sources. Traders should note this distinction matters when comparing forecasts across platforms.

The critical variable between now and August 2026 is the Pacific high-pressure system's positioning during mid-August, which determines whether tropical air masses dominate or whether any frontal activity moderates temperatures. Japan Meteorological Agency seasonal outlooks and real-time upper-atmosphere patterns in late July 2026 will signal the likely range. The settlement window closes at midday UTC on 18 August, meaning Tokyo's morning and early afternoon readings will determine the outcome before European trading hours conclude.

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 Prediction Today. 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%.