Highest temperature in London on June 22?

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Market context

London City Airport’s daytime high will be set by how far the current heat spell peaks before the market’s 12:00 UTC settlement window closes, with local forecasts already pointing to a very warm Monday and an escalation through the week. BBC Weather had London City Airport at 28°C for Monday 22 June, rising to 34°C on Tuesday and 36°C on Wednesday, while the Met Office forecast for the station showed a maximum of 30°C with showers developing later on Monday.[2][6]

A 0% crowd-implied chance on the YES side suggests the market is pricing in almost no probability that the day’s top reading lands in the relevant range, but comparable June heat events in London have produced sharp upside when hot air arrives early and clouds or showers hold off. The Standard reported warnings that the capital could reach 39–40°C later in the week, underlining that forecasters were already treating this as an unusually strong early-summer setup rather than a normal June pattern.[1] Weather Underground’s daily history page for EGLC will be the settlement source, so the key variable is the single highest recorded temperature at London City Airport on the calendar day, not the average or the evening close.[8]

For traders, the main catalysts are the timing of the hottest part of the day, any thunderstorm or sea-breeze effects that cap the maximum, and whether updated forecasts keep trending hotter into the afternoon. At 14:21 UTC, the observed temperature at London City Airport was 13°C with southerly winds, humidity at 88% and falling pressure, which is a reminder that morning conditions can look very different from the eventual peak if the boundary layer rapidly warms later on.[2] On-chain, this kind of weather market typically settles in USDC, so positioning can move quickly if late forecast revisions change the implied odds before the cutoff.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reads Highest temperature in London on June 22? on-chain. Polymarket's quote comes directly from the Polygon order book — the only comparable venue with on-chain settlement. Kalshi (USD, off-chain), Betfair (GBP/EUR, off-chain) and Manifold (play-money) are listed for comparison. Every CTA routes to BTC Prediction, which mirrors the Polymarket order book directly.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

FAQ

Where can I trade this market with the lowest fees?

On BTC Prediction, 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?

BTC Prediction 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 BTC Prediction?

Zero. BTC Prediction 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.