Highest temperature in London on August 10?

Platform comparison

Market context

London’s highest temperature on 10 August is trading against a forecast that currently centres on the mid-20s Celsius, with the market itself split almost evenly between **26°C** and **27°C** at 43% each and only a 10% chance on **28°C**. That is materially less bullish than the broader weather outlook: AccuWeather’s London forecast shows a daily high of **81°F** for 10 August, roughly **27°C**, while the market description makes clear that the winning outcome will be the highest figure in Weather Underground’s **Daily Observations** table for London City Airport, not the summary high/low panel[1][6].

Historically, London’s August temperatures often sit in the low-to-mid 20s Celsius, and the airport station can differ from central-London readings enough to matter at the margin. The long-run August averages for London place the day’s typical high around the low 20s Celsius, while the station record context shows that extreme August heat is possible but uncommon; the UK’s hottest August day on record was set on 10 August 2003, when readings in the south-east climbed well above 38°C, far outside the range implied here[7][8][15]. Against that backdrop, a 0% YES price implies the crowd sees the named threshold as effectively impossible, but the contract’s actual payoff still turns on a single station observation and the exact temperature bucket used at settlement[6].

The main catalysts are operational rather than event-driven: traders need the London City Airport observation stream to print cleanly before the settlement cutoff, and later revisions to temperatures inside the market window can still matter until the first datapoint for the following date appears[6]. There is no competing policy announcement or scheduled release likely to move this contract; instead, the relevant dependencies are the live Weather Underground table, any late-morning warming or cooling trend, and whether the station reports a maximum that lands on the boundary between adjacent ranges. In cross-platform terms, the gap is stark: the crowd on Polymarket is pricing a near-even 26/27°C split, while the market-wide YES probability remains at 0%, which suggests either a contract-specific wording effect or a serious mismatch between range interpretation and the settlement source[6].

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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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.

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.

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.