Highest temperature in London on June 9?

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Market context

On 9 June 2026, the highest temperature recorded at London City Airport will fall into one of several discrete ranges, with traders currently pricing all outcomes at zero probability on Polymarket. The settlement mechanism relies on historical weather data from Wunderground's London City Airport station, converted to Celsius, creating a straightforward factual resolution once the day concludes. USDC conditional tokens on Polygon will reflect whichever temperature band captures the actual peak reading, making this a pure weather-data arbitrage rather than a forecast of meteorological conditions.

London's June temperatures have historically clustered between 18°C and 24°C, with occasional spikes to 26–28°C during high-pressure systems. The 0% crowd probability suggests either thin liquidity or genuine uncertainty about which specific range will resolve. June 2026 forecasting remains inherently difficult this far ahead; seasonal patterns favour mild warmth rather than extremes, though the UK Met Office's long-range outlook for early summer 2026 will sharpen expectations as the date approaches. Previous June heat waves—such as the 2022 event that pushed London toward 35°C—remain statistical outliers rather than the norm.

Traders should monitor the Met Office's monthly forecasts from April 2026 onwards and track any atmospheric blocking patterns or heat dome developments in late May. The settlement window closes at 12:00 UTC on 9 June, meaning the highest temperature recorded across the full calendar day determines the outcome. Any unusual weather systems developing in the North Atlantic during May–early June could shift probabilities materially, particularly if ridge-building high pressure establishes itself over the British Isles.

Methodology

We track Highest temperature in London on June 9? on the five venues with material liquidity for prediction markets. Live odds come from the Polymarket Polygon order book — the only source that ships real-time data under an open licence. For Kalshi, Betfair and Manifold we list platform attributes (fee, KYC, settlement, payment) instead of fabricated odds, because their APIs use non-comparable contract definitions.

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 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.

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.

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.