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 and resolved against historical weather data. The 0% crowd probability suggests traders expect the outcome to fall outside whichever temperature band this market has defined, though the specific threshold remains unclear from the settlement criteria provided. Cross-platform comparison reveals minimal activity; traditional weather forecasting services and sportsbook weather derivatives show no meaningful divergence, largely because July temperature ranges in Chicago are well-established and predictable at a six-month horizon.

Historical precedent frames expectations sharply. Chicago's July average high sits near 27°C (81°F), with extreme heat days occasionally reaching 32–35°C (90–95°F). The city's record July temperature stands at 39°C (102°F), set in 1995 during an exceptional heatwave. Trader positioning at 0% suggests the market's defined range either captures the statistical centre of July outcomes or sits at an extreme tail—most likely the latter, given typical crowd behaviour in weather markets. Without visibility into the exact temperature brackets offered, the probability reflects either conservative expectations or a range so narrow that near-normal conditions would resolve outside it.

The National Weather Service's seasonal outlook, updated monthly, will provide the primary catalyst for position shifts. Long-range climate models through June 2026 will signal whether anomalous heat or cooler-than-normal patterns are expected. Any significant revision to summer forecasts—driven by sea-surface temperatures, atmospheric patterns, or El Niño status—could shift implied probabilities materially. Until such signals emerge, the 0% reading likely reflects baseline statistical expectations rather than conviction about extreme outcomes.

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?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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.