Highest temperature in Madrid on June 28?

Platform comparison

Market context

The underlying event is the peak daily temperature at Madrid-Barajas Airport on 28 June 2026, a date that historically marks the onset of Madrid’s most intense summer heat. Long-term averages suggest daytime highs near 28°C, yet the current crowd-implied probability of 0% for a high-temperature outcome ignores the region’s volatile recent trajectory. In June 2019, the airport recorded 40.7°C on exactly 28 June, the highest for that date in over a century[6]. This year, Spain has already shattered multiple June records, with Cantabria hitting 43.7°C and Andujar reaching 45.1°C, signalling a heatwave of unprecedented scale[3][9].

The consensus leans heavily toward moderate temperatures, assuming the historic 28°C average will hold, but value likely sits contrarian, betting on the heatwave’s persistence. Traders should monitor the European Heatwatch network’s daily bulletins and the AEMET (Spanish Meteorological Agency) forecasts for 27–28 June, which will confirm whether the current ridge extends over Madrid. Recent reports indicate hundreds may have died from this week’s record heat, underscoring the system’s severity and the high risk of extreme temperatures persisting into late June[4]. The underdog here is the moderate-temperature scenario; the favourite is a breakout above 35°C, driven by the same atmospheric conditions that have already broken records across the Iberian Peninsula.

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

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

Is this market available outside the US?

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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?

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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.