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 records. The 0% crowd-implied probability reflects the market's current state, though this represents a settlement window that extends through midday on the date itself, allowing real-time temperature data to determine the final outcome.

Chicago's July temperatures typically range from 75°F to 88°F, with historical highs occasionally exceeding 95°F during heat waves. The city's record July temperature stands at 104°F, set in 1934 during the Dust Bowl era. More recently, July 2019 saw a peak of 96°F at O'Hare, whilst July 2022 reached 94°F. These comparables suggest that extreme heat—above 95°F—occurs in roughly one-third of July months, making the distribution of possible temperature ranges material to understanding where traders should position themselves across available brackets.

The National Weather Service Chicago office will issue forecasts through late July 2026, with particular attention to upper-level atmospheric patterns and any heat dome development in the preceding weeks. Traders should monitor mid-July weather models and any heat advisories issued by the NWS, as these typically signal conditions favourable for temperatures exceeding seasonal norms. The settlement mechanism depends entirely on Wunderground's historical data feed from KORD, which records hourly observations; any data gaps or station maintenance would require cross-reference with backup National Weather Service records. Current divergence between prediction markets and traditional weather forecasting remains minimal at this distance from the event date.

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

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 PolyGram. 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 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.