Highest temperature in Tokyo on July 9?

Platform comparison

Market context

Tokyo faces its annual peak heat window as July 9 approaches, with the specific question for traders being whether the official high at Haneda Airport will land exactly on 29°C. While the Polymarket contract for this single temperature band shows a 31.5% implied probability, the broader market implies a 68.5% chance the reading falls outside this narrow range, either lower or higher. This fragmentation creates a distinct divergence from the 0% YES probability currently implied for a generic "highest temperature" binary contract, highlighting how specific outcome markets often carry higher volatility than broad directional bets.

Historical July data for Haneda shows maximums frequently clustering between 27°C and 32°C, making 29°C a plausible but not dominant outcome. Recent record-breaking heat in Japan, including a national high of 41.2°C recorded in Tamba City in late July 2025, suggests that extreme outliers remain possible even in typical summer windows [7]. The current pricing reflects a plurality rather than a majority, meaning the market expects the temperature to likely deviate from this specific integer, a pattern consistent with previous multi-band weather contracts where the favourite outcome rarely exceeds 35% probability.

Traders should monitor the latest Japan Meteorological Agency forecasts, which publish daily updates that can shift prices sharply before the 12:00 UTC settlement. Current seven-day models from the Met Office project a maximum daytime temperature of 31°C for Haneda, directly challenging the 29°C favourite and suggesting the NO side may hold stronger fundamental support [2]. AccuWeather’s monthly outlook for July 2026 further indicates daily highs ranging from 24°C to 33°C, reinforcing the view that the 29°C band is a narrow target within a wider, volatile distribution [5].

Sources: 1 · 2 · 3 · 4 · 5

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

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.

FAQ

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.

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.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like PolyGram trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.