Highest temperature in Madrid on July 3?

Platform comparison

Market context

Madrid is currently bracing for an intense summer heatwave from July 2 to 5, 2026, with daytime temperatures forecast to soar to 42°C or higher, far exceeding typical seasonal norms. This extreme event, described by weather forecasters as unusually high, means the usual nighttime cool-down will not occur, leaving nights uncomfortably warm above 25°C. The current crowd-implied probability of 0% for the specific temperature range on July 3 appears starkly divergent from the physical reality of this active heatwave, suggesting a significant mispricing compared to analyst consensus on the contract's likelihood.

Historical data frames this anomaly sharply; while July 30 typically stands out as Madrid’s warmest day with an average of 34.1°C, the current 2026 heatwave is already surpassing those figures, with temperatures reaching 40°C in late June and projections of 45.4°C recorded elsewhere in Spain earlier in July. The first six months of 2026 were Spain’s hottest ever recorded, with temperatures 1.6°C above normal, and hundreds may have already died from record heat, indicating a climate baseline that makes the 0% market probability highly questionable against the backdrop of these comparable extreme cases.

Traders must monitor real-time updates from Wunderground for the Adolfo Suárez Madrid-Barajas Airport Station, specifically the highest temperature recorded for all times on July 3, as this is the definitive resolution source. Recent reports from Reuters confirm Spain entered its first official heatwave of 2026 on June 21 with temperatures hitting 40°C, and the Washington Post notes that researchers projected 212 excess deaths from the ongoing wave, underscoring the severity of the catalysts driving this weather event. The divergence between sportsbook lines and this prediction market implies a need to watch for immediate temperature spikes during the 12:00 to 18:00 window when the sun is strongest.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Madrid on July 3? 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

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

FAQ

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.

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.