Highest temperature in Madrid on July 3?

Platform comparison

Market context

Madrid is currently gripped by an intense heatwave from 2 to 5 July 2026, with daytime temperatures forecast to soar to 42°C or higher, far exceeding typical seasonal norms for the city. This extreme event frames the current crowd-implied probability of 0% YES for the highest temperature on 3 July, as the consensus assumes the peak will occur later in the window or that the market resolution threshold is unattainable. Historically, 30 July stands out as Madrid’s warmest day in July with 34.1°C, yet the 2026 anomaly dwarfs this, with the first half of the year already recorded as Spain’s hottest since records began, pushing temperatures 1.6°C above normal levels[7].

Traders must watch for Saharan air mass movements and official heatwave declarations, as these catalysts can abruptly shift temperature peaks within the settlement window. Reuters reported on 21 June that Madrid struggled with temperatures reaching 40°C during the first official heatwave of 2026, indicating a pattern of escalating extremes that could push 3 July’s peak beyond expectations[4]. The value spot likely sits contrarian to the 0% consensus, as the heatwave’s intensity suggests 3 July could indeed hit the highest temperature range, especially if the air mass intensifies before the weekend. With nights remaining uncomfortably warm above 25°C and no nighttime cool-down, the thermal load is cumulative, increasing the probability of record highs on the earliest peak day[1].

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

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

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 Who Will Win. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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 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.

Do I need to KYC for this market?

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

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.