Highest temperature in London on August 5?

Platform comparison

Market context

The London City Airport reading on 5 August is being priced as a near-lock under on the **0% YES** market, which makes the favourite the *no very hot spike* side rather than any specific Celsius band. London’s early-August baseline is usually in the low 20s Celsius: AccuWeather’s August outlook has daily highs mostly between **67°F and 78°F** (about 19–26°C), while long-run August averages sit around **22°C to 23°C** for daytime maxima.[1][12] That leaves the market consensus firmly anchored in mild-summer territory, with the value discussion centring on whether an airport-observed high can squeeze into a warmer bracket if the day runs sunnier and less breezy than expected.

Comparable forecasts point to a modest upside bias, but not a runaway heat case. Multiple 5 August forecasts cluster around **22°C to 25°C** in London, with partly cloudy to sunny intervals and limited rain risk; one source has **25°C** as the day’s high, another puts the range near **25.2°C**, and a third shows a similar spread of **24.3°C to 25.7°C** across model outputs.[2][4][14] On that framing, the contrarian angle is that the crowd may be overconfident in a cooler band if the airport site benefits from a stronger afternoon lift than central-London averages, while the favourite remains the lower-temperature range because the broader consensus is still for a pleasantly mild day rather than a heat event.[2][4][12]

The main catalysts are the midday-to-afternoon weather evolution and any last-minute forecast shifts in cloud cover, wind and precipitation, because those determine the day’s absolute peak before the settlement window closes at noon UTC. A sunnier, calmer afternoon would favour the upper end of the forecast range; more cloud or a sea-breeze-style cap would keep the high pinned near the low-20s. Current forecast services already flag low rain odds and some breeziness, which matters because gustier conditions can limit surface heating at an exposed airport station.[2][5]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on August 5? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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 Who Will Win 2026. 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.

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.