Highest temperature in Madrid on July 3?

Platform comparison

Market context

Madrid is locked into an intense heatwave today, with temperatures soaring to dangerous levels across central Spain and scorching daytime heat persisting through the forecast period[2]. The crowd-implied probability of 0% for the highest temperature falling in the lowest range reflects the reality that July 3, 2026, is not a cool day; forecasts show daily highs ranging from 90° to 103°F (32° to 39°C), with the average high for July sitting at 95°F (35°C)[1]. Historical context reinforces this: Spain recorded its hottest day since 1928 on July 18 at 45.4°C, and temperatures above 43°C have been common in multiple regions during recent heatwaves[4]. Even the typical warmest day in July, July 30, reaches 34.1°C, making a low-temperature outcome statistically implausible[7].

Traders should monitor the official heatwave declarations and energy demand announcements, as the current pattern is expected to persist through the forecast window with no relief in nighttime cooling[2]. The first official heatwave of 2026 was declared on June 21, when Madrid hit 40°C, and subsequent warnings indicate daytime temperatures could reach 42°C or higher[3]. Recent data suggests over 200 excess deaths in Spain from this unprecedented heat, highlighting the severity of the event and the likelihood of extreme readings continuing[5]. With the first half of 2026 already recorded as Spain’s hottest ever, the atmospheric conditions are primed for record-breaking highs rather than modest temperatures[6]. Watch for updates from the national meteorological agency regarding the duration of the heatwave, as persistence is key to the settlement outcome.

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

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

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 Prediction Today. 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.

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.

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.