Highest temperature in London on June 9?

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Active sub-markets

Market context

On 9 June 2026, the highest temperature recorded at London City Airport will settle this market into one of several temperature bands. The settlement hinges on a single daily maximum reading from Wunderground's historical data feed for that specific station, with the crowd currently assigning zero probability to any outcome—a common state for markets opening far in advance of the event date.

London's June temperatures typically range between 18°C and 24°C, though heat waves occasionally push readings above 28°C. The Met Office's 30-year climate averages show a June mean of around 20°C for central London, with extremes on record reaching 32°C in June during the 2022 heat event. Historical volatility matters here: traders comparing Polymarket's implied probability display against Kalshi's decimal odds format will notice the same underlying uncertainty, though Kalshi's UK regulatory framework and lower fees (typically 2–5% versus Polymarket's variable structure) may shift participation patterns. Betfair and Smarkets, with their established weather-betting user bases, sometimes show tighter spreads on similar meteorological events, though liquidity on specific temperature bands varies significantly.

The key catalyst is the UK summer weather pattern emerging in late May and early June 2026. Atlantic pressure systems, jet stream positioning, and any blocking high-pressure systems over continental Europe will determine whether June 9 falls into a cool, typical, or anomalously warm scenario. Traders should monitor the Met Office's extended forecast window (issued around late May) and any official heat-health alerts, which typically trigger when temperatures exceed seasonal norms by significant margins. Current zero probability likely reflects the market's early stage rather than genuine certainty about the outcome.

Methodology

This page compares Highest temperature in London on June 9? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. Live odds come from the Polymarket order book; the other venues' contract details are maintained manually because their APIs aren't directly comparable. Every CTA routes to Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Where can I trade this market with the lowest fees?

On Kalshi Alternative UK, 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?

Kalshi Alternative UK 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.

What does it cost to trade on Kalshi Alternative UK?

Zero. Kalshi Alternative UK routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

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.