Highest temperature in Madrid on July 3?

Platform comparison

Market context

Madrid is currently bracing for an intense heatwave from July 2 to 5, 2026, with daytime temperatures forecast to soar to 42°C or higher, far exceeding typical seasonal norms for the city. This extreme event places the current crowd-implied probability of 0% for the highest temperature on July 3 at aBarajas Airport in stark divergence from the real-world meteorological reality, where analysts and weather forecasters explicitly warn of record-breaking highs. Historical data shows that while July 30 is traditionally Madrid’s warmest day at 34.1°C, the 2026 heatwave has already pushed temperatures in late June to 40°C, with Reuters reporting that hundreds may have died from the record heat earlier in the month, suggesting a significant upward shift in baseline expectations.

Traders should monitor the official heatwave declarations and daily temperature updates from Wunderground for the Adolfo Suárez Madrid-Barajas Airport Station, as these will directly determine the market resolution. The settlement window ends on July 3, 2026, at 12:00 UTC, meaning any temperature spike during the hottest part of the day, between 12:00 and 18:00, will be critical. Recent news from the weather agency confirms that the first six months of 2026 were Spain’s hottest ever recorded, with temperatures 1.6°C above normal, reinforcing the likelihood that July 3 will see temperatures well above the 34°C threshold implied by traditional climate models. The divergence between sportsbook lines, which may still reflect historical averages, and the prediction market’s 0% probability highlights a potential mispricing given the current extreme conditions.

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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

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 Best Prediction Markets. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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.