Highest temperature in London on June 28?

Platform comparison

Market context

The real-world event driving this market is the peak daily temperature recorded at London City Airport on 28 June 2026, a date that historically sits within the UK’s warm season. Current crowd-implied probability of 0% for any outcome above the lowest range suggests traders expect a cool day, yet this contradicts seasonal norms where average highs exceed 67°F from mid-June through early September[4]. A programmatically approaching trader would first benchmark this against comparable cases: on 6 June 2026, the same airport recorded 17°C with 100% market certainty for that range, while recent heatwaves have pushed London temperatures to 35.1°C and even 40.2°C at Heathrow[1][7][9]. The 0% probability today appears anomalous given that BBC Weather forecasts a high of 26°C for London City Airport on this date, with sunny intervals and light southerly winds[2].

Traders should monitor immediate meteorological dependencies rather than waiting for official settlements, as Wunderground will resolve the market using real-time station data available via its daily history portal. Key catalysts include the Met Office’s extreme heat warning status, which was recently extended to 11:59pm following a record-breaking 35.1°C day in London[7], and the falling pressure trend (1012mb) observed at the airport, which often precedes temperature shifts[2]. A power-user building a conditional order bot would integrate live feeds from the National Weather Service for EGLC, noting the current 25°C reading at 11:42pm UTC[8], and cross-reference with AccuWeather’s forecast of 79°F (26°C) for 28 June[5]. The settlement window ending at 12:00:00Z on 29 June means any late-night temperature spike before midnight could alter the outcome, making real-time API polling essential for accurate positioning.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on June 28? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Polymarket App UK, which mirrors the Polymarket order book at 0% fees.

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 App 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.

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 Polymarket App UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.