Highest temperature in London on June 21?

Platform comparison

Active sub-markets

Market context

The relevant real-world event is the day’s **highest recorded temperature at London City Airport** as logged by Wunderground, so any programmatic read should key off the maximum value published for the station rather than a citywide forecast or a noon snapshot. The market does not resolve until the first data point for the following date is published, which matters for automation because settlement can lag the observed weather by several hours.[1]

For context, late-June London typically sits near the low 20s Celsius, and the market currently pricing a 0% YES suggests traders are treating the upper tail as effectively excluded rather than merely unlikely.[1] That is a very different shape from a standard forecast market: the task is not to predict the afternoon temperature, but to infer whether the station’s *daily maximum* will land in the higher bins after accounting for any short-lived spike, especially on a warm, settled day.

A hands-on workflow would watch the latest station forecast from the Met Office and BBC Weather, then compare it with live observations and any heat advisories as the day unfolds.[3][7] A power-user setup can trigger conditional orders if the forecast maximum steps into a higher band, or if observed temperatures are already close to a threshold by early afternoon; in London, changing cloud cover, sea-breeze influence and brief convective bursts can move the daily high enough to shift the winning range.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote (Polymarket), four reference venues with their key attributes, and a single execution path — every trade button routes to Polymarket Review UK, which mirrors the Polymarket order book directly.

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 Review 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.

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.