Highest temperature in London on August 9?

Platform comparison

Market context

Polymarket is currently pricing the London reading as an outright summer-heat bet on USDC-settled conditional tokens on Polygon, with the crowd leaning heavily to the exact temperature band it expects the London City Airport station to print in Weather Underground’s **Daily Observations** table. The contract resolves from the **highest recorded temperature** in that table, not the broader “Day High & Low” summary, so traders are effectively positioning around a station-level maximum rather than a citywide forecast headline.

The market looks loose against historical August norms but tight against a live hot spell. London’s average August high is about 23°C, yet the city has repeatedly reached the low 30s in strong high-pressure setups, including 31.1°C at Heathrow on 3 August 2026 and 34.8°C on 9 August 2003 in London records cited by local weather tracking. Comparable extreme-day markets tend to reprice sharply when the final station observation appears, because a one-degree difference can shift the winning band even if the day already feels broadly “hot”.[10][7][11]

For a trader, the main catalysts are the actual station observations and any late revisions before Weather Underground publishes the next day’s first datapoint, since Polymarket says edits within the settlement window still count until then.[1] The practical watchlist is simple: whether London keeps the heat, whether cloud or sea breeze caps the airport reading below the upper-20s, and whether the day’s peak arrives late enough to be captured in the daily table. The current weather reporting has London around the low 30s on 9 August with sunny conditions and very low rain risk, which is why the market’s pricing sits around the hotter bands rather than the climatological average.[12][1]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to PolyGram, 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

Is this market available outside the US?

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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.

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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.