Highest temperature in London on August 13?

Platform comparison

Market context

The market concerns the highest temperature recorded at London City Airport on 13 August 2026, with settlement based on Weather Underground's Daily Observations table rather than summary figures. The 0% crowd-implied probability reflects the inherent difficulty in predicting precise temperature ranges nearly two years in advance, though this represents an extreme position given that August temperatures in London routinely exceed 20°C and frequently reach the mid-to-high 20s Celsius.

Historical August data from London City Airport shows mean daily highs around 23–24°C, with extremes ranging from 16°C to 32°C across the past two decades. The 2022 heatwave pushed readings above 30°C on multiple days, whilst cooler Augusts have seen highs barely exceed 18°C. This variability means any single-day forecast two years out carries substantial uncertainty, yet the complete absence of YES probability suggests traders may be underweighting the statistical likelihood that temperatures will fall within at least one of the available resolution ranges. Cross-platform comparison reveals prediction markets typically price such weather events with modest but non-zero probabilities, whereas sportsbooks rarely offer temperature contracts at this granularity.

Traders monitoring this contract should track seasonal climate patterns and any emerging consensus from meteorological bodies regarding summer 2026 conditions. The UK Met Office publishes seasonal outlooks approximately three months ahead of the target period, which could materially shift market pricing. Additionally, the specific reliance on Weather Underground's Daily Observations table—rather than alternative weather stations or summary data—creates a technical dependency that resolvers should verify independently before settlement.

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 Kalshi vs Polymarket. 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 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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.