Highest temperature in Tokyo on August 15?

Platform comparison

Market context

Tokyo's highest temperature on 15 August 2026 will be measured at Haneda Airport Station and recorded in Weather Underground's Daily Observations table, with settlement contingent on that specific data source rather than summary figures. The Polymarket contract currently prices at 0% YES across all temperature bands, reflecting either extreme confidence in a particular outcome or minimal trading activity establishing a floor. USDC settlement on Polygon means traders holding conditional tokens representing temperature ranges will see automatic execution once Weather Underground publishes the official reading.

Historical August temperatures at Haneda provide essential calibration. Over the past decade, mid-August highs have typically ranged between 32–36°C, with 2010 recording 37.9°C as a notable extreme. The 0% probability across all bands suggests traders may be awaiting clearer market segmentation or that the contract's reliance on Weather Underground's Daily Observations table—rather than the Day High & Low summary—creates ambiguity about which reading will ultimately govern settlement. This distinction matters: the two sources occasionally diverge by tenths of a degree, potentially shifting outcomes between adjacent temperature bands.

Traders should monitor Japan Meteorological Agency forecasts from late July 2026 onwards, particularly alerts regarding heat waves or atmospheric pressure systems affecting the Kanto region. El Niño or La Niña conditions developing through 2025–2026 could shift seasonal temperature patterns. The settlement window closes at 12:00 UTC on 15 August, meaning traders have no post-event trading window; the market resolves immediately upon Weather Underground's publication of that day's data.

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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

UK Frequently Asked Questions

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.

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.

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%.