Highest temperature in London on July 9?

Platform comparison

Market context

On 9 July 2026, the London City Airport will record its peak daytime temperature, a single real-world data point that will determine whether a YES or NO share in this prediction market settles as a winner. A YES share represents a bet that the highest temperature falls within a specific range (for example, 32–33°C), while a NO share bets it falls outside that range; odds shift as traders buy and sell based on new weather information. Currently, the market-implied probability for a YES outcome is 0%, suggesting the crowd believes the temperature will not hit the targeted range, even though high pressure over southern England is pushing daytime maxima toward 32°C under mostly settled conditions[1].

Historically, July is London’s hottest month, with London City Airport averaging a high of 72°F (22°C), yet extreme heat events have occurred, such as the 40.2°C record set at Heathrow and St James’s Park in July 2022[2][7]. Current Met Office guidance points to a daytime maximum near 32°C, aligning with market-implied odds favouring a 32–33°C peak, though this remains below the 34°C threshold that currently holds 59% probability in some markets[1]. Traders should monitor hourly updates from Wunderground and Met Office forecasts, particularly any sudden shifts in cloud cover or wind direction that could alter the peak temperature, as these dependencies directly influence the resolution source[4][5]. Recent forecasts from AccuWeather indicate toasty conditions with abundant sunshine for 9 July, reinforcing the likelihood of a high near 32°C but not exceeding 34°C[8].

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

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 Prediction Market UK. 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'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.

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.