Highest temperature in Chicago on July 27?

Platform comparison

Market context

Chicago's peak temperature on 27 July 2026 will be recorded at O'Hare International Airport, the official National Weather Service station for the metropolitan area. The market currently shows 0% implied probability across all temperature bands, suggesting either incomplete pricing or genuine uncertainty about which range will capture the day's high.

Historical July data from O'Hare reveals a median high around 79–82°F, with the record for any July day standing at 97°F (set in 1934). The past decade shows most late-July highs clustering between 75–88°F, though heat waves pushing into the low 90s occur roughly every three to five years. The 2012 heat wave saw Chicago reach 97°F in early July, whilst the cooler summer of 2014 produced July highs rarely exceeding 80°F. This range—from upper 70s to low 90s—frames the realistic outcome distribution; extreme outliers above 95°F or below 70°F remain statistically possible but uncommon for this date.

Traders should monitor the National Weather Service Chicago office's extended forecasts from mid-July onwards, as atmospheric patterns solidify roughly two weeks ahead. The North Atlantic Oscillation and upper-level ridge positioning typically determine whether high-pressure systems deliver heat or whether cooler Canadian air masses dominate the Midwest. Recent climate data through 2025 shows no systematic shift in late-July temperature patterns, meaning historical distributions remain the baseline reference. The settlement window closes at noon local time, so morning forecasts issued on 27 July itself will carry material weight for final positioning.

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Who Will Win, which mirrors the Polymarket order book directly.

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. 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.