Highest temperature in London on August 6?

Platform comparison

Market context

London’s highest temperature on 6 August is being priced like an ordinary late-summer day rather than a heat event, with the contract showing 0% for YES while the visible market bins on Polymarket have already pushed almost all volume into **72–73°F** and treated warmer bands as effectively dead money.[7] That is materially below a typical London August high of about **22°C** and close to the current short-range forecast of roughly **22°C maximum** and **13°C minimum**, which implies a peak in the low-20s rather than the upper-20s or 30s.[8][3] On that reading, the crowd’s implied pricing is notably tighter than the forecast itself, because a broad “mid-20s Celsius” outcome would still fit current weather guidance but is being treated as very unlikely in the market.[1][3]

Comparable context matters here because London’s August climate usually centres on the high teens to low 20s Celsius, and even the city’s warmer summer spells are episodic rather than persistent.[8][13] The Met Office said UK daily maximums in summer 2026 were running above average overall, but not at record seasonal levels, which is consistent with a market that should be sensitive to any late forecast upgrade but not to routine warmth.[15] Traders should watch the London City Airport forecast track, especially any change in cloud cover, wind direction, or shower timing that could lift or cap the afternoon peak before the settlement window closes at noon UTC.[1][3] The main dependency is the final Wunderground history entry for London City Airport, because the contract resolves on the *highest recorded temperature for the full day*, not a scheduled daytime reading.[1]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

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?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like PolyGram trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.