Highest temperature in London on June 28?

Platform comparison

Market context

The real-world event hinges on the highest temperature recorded at London City Airport on 28 June 2026, a date that historically sits within London’s warm season. For a power-user evaluating this market programmatically, the 0% crowd-implied probability for any outcome above the lowest range suggests the algorithmic consensus expects a cool day, likely under 17°C. This reading is framed by comparable cases: in early June 2026, a similar market resolved to 17°C with 100% certainty, indicating that mid-June temperatures in London often hover near this threshold rather than soaring into extreme heat[1].

Traders should monitor the Met Office’s heat warnings and the National Weather Service’s real-time METAR data for London City Airport, as sudden shifts in southerly winds or humidity could alter the forecast. Recent records show London hit 35.1°C on 24 June 2026, breaking previous highs and prompting an extreme heat warning, yet this spike was not sustained at City Airport, where temperatures remained moderate[7]. A programmatically built bot would weight these dependencies heavily, cross-referencing Wunderground’s historical daily data with live METAR feeds to detect anomalies before the settlement window closes[3]. The key catalyst is whether the predicted 26°C high for 28 June[2] materialises or if cloud cover and light winds suppress it, a scenario consistent with the current 0% probability for higher ranges.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on June 28? 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 Polymarket Review UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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.