Highest temperature in Madrid on August 15?

Platform comparison

Market context

On 15 August 2026, Madrid's highest temperature will be recorded at Adolfo Suárez Madrid-Barajas Airport, with traders currently pricing a 2% probability that this reading exceeds 40°C. The market resolves using Weather Underground's Daily Observations table rather than summary figures, a distinction that matters when intraday peaks diverge from official highs. Settlement occurs at 12:00 UTC on the resolution date, giving the market window to capture the full diurnal cycle.

Madrid's August climatology shows extreme heat is routine but not guaranteed to breach 40°C on any given day. Historical data from the airport station indicates that whilst temperatures regularly reach 38–39°C in mid-August, the 40°C threshold represents a meaningful boundary. The city has experienced multiple 40°C+ days in recent Augusts, including the 2022 heatwave when readings exceeded 40°C on multiple occasions; however, individual-day probabilities remain constrained by the specificity of the date and the variability of synoptic patterns across years.

Traders monitoring this contract should track European weather models from mid-July onwards, particularly the positioning of high-pressure systems over the Iberian Peninsula. The Spanish meteorological agency (AEMET) issues routine forecasts that typically become reliable 10–14 days ahead. Any significant Atlantic blocking pattern or heat dome formation would shift probabilities materially. Conversely, unseasonably cool air masses or cloud cover from Atlantic systems could suppress the likelihood further. The current 2% pricing reflects base-rate scepticism about hitting that specific threshold on that specific date, despite Madrid's general propensity for extreme August heat.

Methodology

We track Highest temperature in Madrid on August 15? 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.

UK Frequently Asked Questions

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.