Highest temperature in London on July 4?

Platform comparison

Market context

On 4 July 2026, the highest temperature recorded at London City Airport will determine the outcome of this prediction market, with the current crowd-implied probability of hitting 28°C sitting at 0% YES. This near-zero pricing reflects a stark divergence from historical July patterns at the station, where the average high reaches 22°C (72°F) and extreme heatwaves have previously pushed readings above 40°C, as seen during the July 2022 event when Heathrow recorded 40.2°C[7]. While the 2022 heatwave was brief, the 2025 July event also brought intense temperatures across the British Isles, suggesting that a 0% probability may be overly dismissive of London’s capacity for sudden thermal spikes[9].

Traders should monitor the Met Office daily forecasts and Wunderground real-time updates for the London City Airport station, as these are the definitive resolution sources for the contract[4]. The immediate catalyst is the scheduled weather pattern for Saturday 4 July, which currently shows a forecast high of 15°C (61°F) with moderate humidity and falling pressure, indicating stable conditions unlikely to breach the threshold[1]. However, the thin volume and two-day resolution window create volatility, meaning any sudden shift in the southerly wind flow or pressure systems could rapidly alter the implied probability[10]. USDC liquidity on the Polygon network remains the primary mechanism for positioning, with conditional tokens allowing precise exposure to the temperature range outcome.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on July 4? 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

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.

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.