Highest temperature in Chicago on July 27?

Platform comparison

Market context

Chicago's peak temperature on 27 July 2026 will be measured at O'Hare International Airport, with settlement determined by the highest reading recorded across the full calendar day. Current market pricing reflects near-zero conviction in any single temperature band, suggesting genuine uncertainty about conditions eighteen months forward rather than consensus on a particular outcome.

Historical July data from O'Hare shows the airport typically records highs between 78°F and 88°F during late July, with extreme heat days (above 90°F) occurring roughly once per decade on any given date. The all-time July record for Chicago stands at 97°F, set in 1934. Comparable late-July forecasting windows demonstrate that seasonal norms dominate outcomes—anomalous heat waves or cool spells remain difficult to predict beyond a fortnight, making long-range temperature band forecasts inherently dispersed across multiple scenarios.

Traders monitoring this market should track atmospheric pattern shifts as summer 2026 approaches, particularly ridge positioning over the Great Lakes region and upper-level jet stream behaviour in the weeks preceding late July. The National Weather Service's extended outlooks, typically issued four to six weeks ahead, will provide the first meaningful signal of whether July 27 falls within normal ranges or deviates toward heat or coolness. Seasonal climate oscillations—including potential La Niña or El Niño conditions—may influence broader temperature tendencies across the summer, though their predictive power for a specific date remains limited.

Methodology

We track Highest temperature in Chicago on July 27? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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.

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.

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.