Highest temperature in Chicago on July 27?

Platform comparison

Market context

Chicago's highest temperature on 27 July 2026 will be measured at O'Hare International Airport and resolved against historical weather data. The crowd currently assigns zero probability to any outcome, suggesting either extreme confidence in a particular temperature band or insufficient liquidity to establish meaningful odds.

July temperatures at Chicago O'Hare typically peak between 80–88°F, with the station's all-time July high of 97°F recorded in 1988. Over the past decade, late-July highs have ranged from 74°F to 91°F, clustering around the mid-80s. The 0% implied probability across all ranges signals the market has not yet calibrated; historical volatility in summer weather patterns means the actual high could plausibly fall anywhere within a 15–20°F spread. Traders should examine whether the crowd is simply absent rather than confident in a specific outcome.

The National Weather Service issues extended forecasts roughly 10–14 days ahead, with meaningful precision emerging 5–7 days before 27 July. Atmospheric patterns in late July 2026 will depend on jet stream positioning and any tropical systems affecting the Midwest—factors that remain unknowable at present. The settlement window closes at midday on the event date, allowing only morning observations to count. Early-season heat waves or cooler-than-average patterns developing in mid-July would shift expectations materially, but no such signals exist in current seasonal outlooks.

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 2026. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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 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.