Highest temperature in London on August 8?

Platform comparison

Market context

London’s temperature on 8 August is the event here, and the market is trading **0% YES**, which makes the current price a clear underdog view against the weather set-up. Forecasts published for the day put London in the low-to-high 20s Celsius, with one source showing 28°C for 8 August and another listing 73°F, or about 23°C, alongside cloudy conditions; either way, the consensus sits well above the cool-summer end of the distribution and points to a meaningful chance of a mid-to-high 20s reading rather than a mild day.[3][11][5]

For framing, London’s August average maximum is usually around 22°C, so anything in the 26°C-plus band would already be a warm outcome rather than an outlier, while 28°C would sit comfortably above climatology.[7][13] That is why a 0% YES line looks more like an overcorrection than a true no-hoper if traders are pricing only one narrow band; the value may lie on the hotter brackets if the day bakes in sunshine, or on the middle bands if cloud cover caps the upside. Historical comparison matters because London can swing materially on a single forecast change, and the market resolves from the airport observation table rather than the headline daily summary, so the exact peak matters more than the general city forecast.[11]

The key catalysts are the same ones that move any same-day temperature market: updated short-range forecasts, cloud cover, wind direction, and whether the afternoon stays bright enough to let Heathrow and central London-adjacent stations warm through. On the day itself, the most important dependency is the actual London City Airport observation in Weather Underground’s Daily Observations table, which means late-morning through mid-afternoon readings are the decisive ones for settlement.[11] If the broader warm forecast holds, the consensus should stay tilted to higher temperature bands; if marine cloud or an earlier sea breeze arrives, the contrarian case is that the peak lands lower than the market expects.[3][5]

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.

UK Frequently Asked Questions

Is this market available outside the US?

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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.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

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