Highest temperature in London on August 16?

Platform comparison

Market context

On 16 August 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges, measured in degrees Celsius via Weather Underground's Daily Observations table. The market currently shows 0% implied probability across all temperature bands, suggesting either incomplete pricing or that traders are awaiting baseline forecasts before committing capital. This contract resolves specifically to the Daily Observations data rather than summary figures, a distinction that matters when Weather Underground's different reporting sections occasionally diverge—a technical detail that could affect settlement interpretation if temperatures cluster near range boundaries.

London's August temperatures typically peak between 20–26°C, with historical August 16 records showing considerable year-to-year variation. The 1990 heatwave saw 32.8°C recorded in central London on that date, whilst cooler years have produced highs around 18–20°C. Cross-platform comparison reveals sportsbooks rarely price specific daily temperature outcomes, leaving prediction markets as the primary venue for this contract. Analyst consensus from the Met Office's seasonal outlooks suggests August 2026 could trend warmer than the 30-year average, though such forecasts carry wide confidence intervals this far ahead.

Traders should monitor the Met Office's updated seasonal forecast (typically released monthly) and any Atlantic weather pattern shifts signalling heat dome positioning over the UK. The UK's summer weather remains substantially influenced by jet stream configuration and North Atlantic sea-surface temperatures, both of which show meaningful variation in medium-range models beyond the 10-day horizon. Current 0% pricing likely reflects the market's nascent stage rather than genuine consensus that all temperature ranges are impossible.

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

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 Best Prediction Markets. 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.

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Best Prediction Markets trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.