Highest temperature in Paris on August 4?

Platform comparison

Market context

The underlying event is the highest temperature recorded at Paris-Le Bourget Airport on 4 August 2026, and the market will settle against that station’s daily maximum on Wunderground rather than a citywide average. With the crowd currently pricing 0% for a YES, the contract is effectively being treated as if a qualifying outcome is not expected, even though the live Polymarket board has already been concentrating on the low-30s Celsius band, led by 31°C and 32°C. That gap matters because the resolution is a single-station maximum, not a forecast for central Paris or a broad regional average.[2][12]

Historical context points to a late-summer Paris profile that usually sits in the mid-20s Celsius, with some forecast services describing August highs around 23°C to 26°C on long-run norms. Recent heat has complicated that baseline: Reuters reported that July was France’s hottest ever month, and other reporting in June described repeated record-breaking heat across the country, so a warm one-off spike at an airport station would not be unusual in the current climate regime.[6][8][13] Against that backdrop, the live market’s near-centre of mass around 31°C-32°C is far above climatology, but still consistent with a hot spell rather than an extreme outlier.[2][6]

The key trader watchpoints are the Paris and Île-de-France forecast updates, especially any shift in cloud cover, showers or thunderstorm risk on the morning of 4 August, because those can cap the day’s maximum even when broader regional conditions are warm.[16] Wunderground’s station history is the settlement source, so the last few hours of the local forecast matter more than national commentary, and any divergence between station-specific expectations and the broader weather narrative is where pricing can move most sharply. The current 0% YES reading therefore looks much more defensive than the public forecast consensus, suggesting the contract is trading well below the implied likelihood of a low-30s outcome.[2][16]

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 Kalshi vs Polymarket. 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'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.