Highest temperature in Tokyo on August 19?

Platform comparison

Market context

Tokyo's highest temperature on 19 August 2026 will be measured at Haneda Airport Station and resolved against Weather Underground's Daily Observations table rather than its summary display—a distinction that matters when platforms diverge on data hierarchy. The current 0% implied probability reflects either extreme confidence in a specific temperature band or minimal trading activity; across Polymarket, Kalshi, and Betfair, weather markets often show thin liquidity until the settlement window narrows, making early probabilities unreliable guides to consensus forecasting.

August temperatures in Tokyo typically peak between 32–36°C, with Haneda recordings historically tracking slightly cooler than central urban stations due to proximity to Tokyo Bay. The Japan Meteorological Agency's seasonal outlook and any issued heat advisories in late July 2026 will shape trader positioning. Recent summers have seen increased volatility; the 2023 summer recorded multiple days exceeding 35°C in the capital, whilst 2024 saw more moderate peaks. Traders should monitor JMA forecasts released in early August, which provide 10-day outlooks with reasonable accuracy for temperature ranges.

The resolution mechanism's emphasis on Daily Observations rather than summary highs creates an arbitrage opportunity if traders cross-reference Weather Underground's raw data feeds against other meteorological sources. Kalshi's decimal odds format and Betfair's lay-betting structure may price tail outcomes differently than Polymarket's binary approach, particularly for extreme temperature bands. KYC requirements vary across platforms—Polymarket's lighter verification versus Kalshi's stricter US-focused compliance—affecting which markets attract international volume and thus liquidity depth on niche weather events.

Methodology

We read Highest temperature in Tokyo on August 19? 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

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.

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

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.

Which platform is accessible globally?

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

Are all these platforms regulated?

No. Kalshi is CFTC-regulated (US). Betfair and Smarkets are UK Gambling Commission licensed. Polymarket operates without explicit regulation — a different risk profile than a regulated sportsbook.