Highest temperature in London on June 21?

Platform comparison

Active sub-markets

Market context

London City Airport’s highest temperature on 21 June is the key print, and the market is currently pricing **0% for YES**, which leaves the field heavily skewed towards the under. With the settlement source being the day’s peak reading at EGLC on Wunderground, the favourite is plainly a low-temperature bucket, while any upside outcome depends on a late burst of warmth rather than the midday forecast alone. At 23:54 UTC, BBC Weather shows London City Airport at **13°C** with southerly wind, high humidity and falling pressure, which is a modest starting point rather than a setup for an obvious heat spike.[1]

Historically, late-June in London is warm enough to produce a wide distribution, but not so hot that extreme prints are routine. WeatherSpark says the warm season in London runs from mid-June into early September, with average daily highs above 67°F, so the consensus shape is for a middling summer day rather than a freeze or a scorcher.[3] That matters for handicapping: with the market at zero on YES, the crowd is effectively saying a higher-than-expected temperature bucket is the underdog. The value question is whether the current setup underprices a brief evening or afternoon spike; if the day finishes near the current observation, the lower bands remain the favourite, while any contrarian case needs a much warmer intraday high than the present reading suggests.[1][3]

The main catalyst is the evolving local forecast and whether any heat warning or clearing trend lifts the ceiling before the London City Airport history page locks in the final max. AccuWeather’s forecast for London City Airport showed an **Amber Warning for Extreme Heat** with a projected high of **82°F/27.8°C** for Sunday, which is exactly the sort of input that can move the upper-temperature buckets from fringe to live if it verifies in the station data.[6] The trader’s watchlist is therefore simple: the near-term forecast, any official Met Office updates, and whether the airport station actually prints above the current observed 13°C base before the settlement window closes.[5][6]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote (Polymarket), four reference venues with their key attributes, and a single execution path — every trade button routes to Who Will Win, which mirrors the Polymarket order book directly.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Where can I trade this market with the lowest fees?

On Who Will Win, which mirrors the Polymarket order book at 0% fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Who Will Win is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

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.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, Who Will Win triggers a quick verification flow that finishes in 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.