Highest temperature in London on June 4?

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Market context

On 4 June 2026, London City Airport's weather station will record a daily maximum temperature in Celsius, and this market resolves to whichever range bracket contains that figure. Polymarket currently prices all temperature bands at 0% YES across the board, reflecting either insufficient liquidity or a technical settlement lag rather than genuine confidence that no temperature reading will occur. The settlement window closes at midday UTC on the day itself, giving traders a narrow window to adjust positions once morning forecasts firm up.

Historical June weather at London City Airport shows daily highs typically ranging between 18–23°C, with occasional warm spells pushing toward 25–26°C. The Met Office's 30-year climate normals place the June average maximum at approximately 21°C. Extreme heat events—temperatures exceeding 28°C in early June—remain uncommon but not unprecedented; the 2022 heatwave saw June temperatures climb unusually high across south-east England, though that occurred later in the month. These precedents suggest the lower temperature brackets (18–21°C range) carry historical weight, whilst higher bands require either an unseasonable warm front or a freak early-summer heatwave.

Traders should monitor the UK Met Office's extended forecast from late May onward, particularly any alerts for high-pressure systems or Atlantic warm air advection moving into the south-east. The Copernicus Climate Change Service and European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble models, updated weekly, will provide the most reliable guidance on whether June 4th falls within a typical spring-to-summer transition or an anomalous warm period. Any official heat-health alert issued in the days before settlement would signal material upside to warmer brackets.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). The odds column is filled only where we have clean data — that avoids the made-up numbers that get a network demoted when search engines cross-check against the source venue.

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?

On Polymarket Scam?, 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.

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.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, Polymarket Scam? 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.