Highest temperature in Tokyo on June 30?

Platform comparison

Market context

The underlying event is the peak daily temperature recorded at Tokyo Haneda Airport on 30 June 2026, a date that historically sits at the cusp of Tokyo’s hot season. Current crowd-implied probability for any specific high-temperature range is 0% YES, suggesting the market views the outcome as either impossible or so uncertain that no range commands confidence. This divergence from sportsbook-style odds—where analysts typically assign non-zero probabilities to extreme heat in late June—raises questions about whether the market is underestimating the likelihood of a record-breaking day or overreacting to data gaps.

Historical precedents frame this probability sharply: Japan recorded its highest-ever temperature of 41.2°C in Tamba City in July 2025, following the hottest June on record, while Tokyo itself logged 41.8°C in a separate heatwave [2][6]. Even at Haneda, June 2026 forecasts predict daily highs between 28°C and 30°C (80–86°F), with the average high for June at 28°C [4][9]. The hot season officially begins 29 June, meaning 30 June is the first full day of peak summer conditions, increasing the chance of anomalous heat [5]. Traders should monitor the Japan Meteorological Agency’s daily heat advisories and Wunderground’s real-time updates for Haneda, especially given the recent record of 10 consecutive days above 35°C in Tokyo [10]. Any sudden spike in humidity or wind patterns could act as a catalyst for extreme temperatures, making the 0% probability appear increasingly fragile as settlement nears.

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.