Highest temperature in London on June 21?

Platform comparison

Active sub-markets

Market context

Polymarket is pricing the **highest recorded temperature at London City Airport** on 21 June through a USDC-settled, Polygon-based conditional-token contract, and the book is currently split around the low 30s with **0% YES** implied for the way the market is framed today.[1][3] The key practical detail is that settlement depends on the Wunderground daily history page for London City Airport, and the market cannot resolve until the first data point for the following day has been published there.[1][3]

For context, late-June London usually sits near the low 20s Celsius, so outcomes in the high 20s or 30°C range require a meaningful warm spell rather than a normal summer afternoon.[1][5] That makes the current pricing much more sensitive to actual observed station highs than to generic London forecasts. On Polymarket, that means traders are effectively holding a live view on whether the airport station prints an unusually hot maximum before the settlement cut-off, not on headline city conditions in general.[1][3]

The main catalysts to watch are the day’s Met Office and BBC Weather updates for London City Airport, because they shape expectations for the station-specific maximum that eventually feeds into the Wunderground record.[4][7] The latest available forecast shows a warm setup, with the Met Office posting a maximum daytime temperature of 28°C and BBC Weather showing 13°C at observation time, but the contract only resolves off the recorded daily high, so any late-afternoon peak or sea-breeze change can still move the final bucket.[4][7]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on June 21? 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 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?

Polymarket 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.

What does it cost to trade on Polymarket UK?

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

Do I need to KYC for this market?

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