Highest temperature in London on August 9?

Platform comparison

Market context

London City Airport’s highest reading on 9 August will be measured against a very warm late-summer baseline, but the contract is resolving to a specific station observation rather than a citywide forecast. London’s long-run average high for 9 August is about 21°C, while recent forecast services and weather history pages have pointed to highs in the high 20s or low 30s Celsius for this date, with one source showing 29.8°C and another 32°C as the expected peak.[2][4][9] Against that backdrop, a 0% yes price appears disconnected from the weather regime implied by the broader market and from the unusually hot conditions recorded in past London August spells.[11][13]

Comparable August cases suggest traders should focus less on seasonal averages and more on whether the airport station gets an exact reading above the contract’s threshold before the noon UTC settlement cut-off. London has a long history of 30°C-plus days in early and mid-August, and 9–10 August 2003 remains the benchmark hot spell for the month, with 38.5°C set at Faversham and 36.0°C recorded in London on 9 August that year.[8][11] More recently, the 2026 heatwave pattern across southern England has produced regional highs in the low 30s Celsius, including 30.6°C at Frittenden and commentary that London and the South East peaked around 31–32°C on 9 August, which is materially above a zero-implied price if those conditions carry through to the airport sensor.[13]

The key catalysts are the final station observations on Weather Underground and any late revision before the first datapoint for 10 August, because the market explicitly uses the Daily Observations table as the primary source.[5] The trader focus is therefore on whether London City Airport’s maximum makes it into the relevant temperature band before the settlement window closes at 12:00 UTC, rather than on any broader headline forecast. Polymarket’s contract page already shows a decisive crowd view centred on 31°C, and that sits closer to weather forecaster guidance than to the current 0% YES implied by the ask side, suggesting a meaningful gap between venue pricing and the weather setup.[5][6][7]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on August 9? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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

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 PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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.