Highest temperature in London on June 19?

Platform comparison

Active sub-markets

Market context

Polymarket is pricing the London City Airport high for 19 June in the low-30s Celsius, with **31°C** the leading outcome on the contract page at **53%** and **30°C** close behind at **44%**. The market settles in **USDC** on **Polygon**, via conditional tokens, so the practical question for a trader is not whether London feels hot, but which Celsius bracket Wunderground ultimately logs as the day’s maximum for **EGLC** before the settlement window closes. [1]

For context, this is a threshold-style weather market: small shifts in the day’s peak temperature can move value between adjacent bins, especially when the front-runner and the next outcome are only a few points apart. Similar London temperature markets have often clustered tightly around the likely daily high rather than breaking far away from forecast guidance, and the same pattern is visible here with the probability mass concentrated around 30–31°C rather than spread across the full range. BBC Weather’s forecast for London City Airport on Friday 19 June pointed to a sunny day, while current observation data showed mild conditions earlier in the day, which is consistent with heat building later rather than an early peak. [1][3]

The main catalysts to watch are the intraday weather path, any last-minute cloud or shower development, and the timing of the highest reading at the airport station, because the market’s source is the recorded daily maximum rather than a citywide average. The market page also notes that it cannot resolve until the first data point for the relevant date has been published on Wunderground, so late updates can matter even after the afternoon has passed. [1]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on June 19? 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

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 Legit?, 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.

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.

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.