Highest temperature in Madrid on July 21?

Platform comparison

Market context

Madrid is set to experience peak summer heat on 21 July 2026, with the Adolfo Suárez Madrid-Barajas Airport Station expected to record a daily maximum between 37°C and 41°C as a major heatwave sweeps central Spain. The current crowd-implied probability of 0% for the market’s default outcome appears misaligned with forecast data, which projects daytime highs in the region reaching 37 to 41°C, significantly higher than the implied null scenario [2].

Historical July patterns in Madrid typically see temperatures clustering around 35–38°C, but the 2026 event is an outlier driven by a sustained heatwave pushing southern and central Spain to extremes of 43–46°C by late July [2]. Programmatic traders should note that the frontrunner outcome is 37°C at 66% probability, with 38°C as the next closest at 28%, suggesting the market is pricing a high-temperature range rather than a failure to reach heat thresholds [1].

Key catalysts include the weekly heatwave forecast updates and real-time Wunderground data feeds, which will determine settlement. Traders building bots or conditional orders should monitor the fourth-week forecast trend, where cloud cover and storms may begin to reduce temperatures in eastern areas, though central Madrid remains locked in extreme heat [2]. The resolution source is fixed to Wunderground’s daily history for LEMD, making automated scraping of that endpoint a viable strategy for position management.

Sources: 1 · 2

Methodology

This page reviews Highest temperature in Madrid on July 21? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi Fees, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

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 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Kalshi Fees trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.