Highest temperature in Tokyo on June 30?

Platform comparison

Market context

The real-world event centres on the highest temperature recorded at Tokyo Haneda Airport on 30 June 2026, a date that historically falls within Japan’s peak summer heatwave. Current crowd-implied probability of 0% YES suggests traders believe the temperature will not reach the threshold defining the “YES” outcome, likely a range above 35°C or similar. This aligns with recent patterns: in 2025, Japan recorded its highest-ever temperature of 41.2°C following the hottest June in history[4], and Tokyo logged a record 10 consecutive days above 35°C in August 2024[8]. Haneda’s June 2026 forecast projects daily highs between 75°F and 83°F (24°C–28°C)[2], with an average high of 80°F (27°C), indicating that while heat is expected, extreme extremes may be less probable than in prior record years.

Traders should monitor the Japan Meteorological Agency’s daily heatwave advisories and Wunderground’s real-time updates for Haneda, as sudden shifts in cloud cover or sea breeze can alter peak temperatures. A recent report from Anadolu Agency noted Tokyo’s record June temperature of 36.4°C in 2024, underscoring the volatility of summer peaks[10]. Platform comparisons reveal key divergences: Polymarket uses decimal odds with lower fees but no KYC, whereas Kalshi and Betfair require identity verification and offer implied probability pricing with higher transaction costs. Smarkets and Betfair also differ in fee structures, with Smarkets charging a commission on winnings only. These structural differences affect liquidity and risk assessment for this specific weather market, where timing and data accuracy are critical.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We read Highest temperature in Tokyo on June 30? from four platform perspectives: Polymarket (on-chain CLOB), Kalshi (CFTC-regulated exchange), Betfair Exchange (sports book exchange), Smarkets (peer-to-peer betting exchange). Polymarket's live mid is the canonical probability; the side-by-side columns benchmark fees, KYC, settlement currency and deposit rails so you can choose the venue that fits your jurisdiction and trade size.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Robinhood Prediction Markets has a different geo footprint and routes to Polymarket's order book at 0% fees.