Highest temperature in Tokyo on August 21?

Platform comparison

Market context

Tokyo's highest temperature on 21 August 2026 will be measured at Haneda Airport Station and recorded in Weather Underground's Daily Observations table, with settlement occurring at midday UTC. The current zero probability assigned across major platforms suggests either extreme confidence in a specific temperature range or minimal trading activity on this particular date-and-location combination. August in Tokyo typically sees highs between 32–35°C, though extreme heat events have pushed readings above 37°C in recent summers.

Historical August temperatures at Haneda provide the baseline for calibration. The station recorded 37.5°C on 16 August 2023 during a broader heatwave, whilst the 2010 peak of 39.5°C remains the modern record for the metropolitan area. Japan Meteorological Agency data shows August 21 specifically has averaged around 33–34°C over the past two decades, with variability driven by Pacific high-pressure systems and typhoon proximity. Traders should note that Polymarket, Kalshi, and Betfair may display these probabilities differently—Kalshi uses decimal odds whilst Polymarket shows implied percentages—creating apparent divergence in how the zero probability reads across platforms, though the underlying liquidity remains sparse.

The Japan Meteorological Agency typically issues extended forecasts 10–14 days ahead, with updates sharpening in the final week before 21 August. El Niño or La Niña conditions active in mid-2026 will influence seasonal temperature patterns. Traders should monitor JMA advisories and any tropical system development in the Western Pacific, as typhoon activity can suppress peak temperatures significantly. Resolution hinges entirely on the Daily Observations table rather than summary highs, a distinction that may create discrepancies worth tracking as settlement approaches.

Methodology

This page compares Highest temperature in Tokyo on August 21? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi Alternative, which mirrors the Polymarket order book at 0% fees.

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.

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.

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. Kalshi 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.