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 and resolved against historical Weather Underground data. The settlement window closes at midday UTC, meaning traders must account for the full diurnal cycle occurring across Central Time before the market locks. This timing creates a practical constraint: the highest temperature typically occurs in mid-to-late afternoon local time, so the reading will be available before settlement, but only if Weather Underground's historical archive updates on schedule.

July temperatures at O'Hare cluster around 79–84°F for daily highs, with extremes ranging from 71°F to 97°F across the historical record. The 0% crowd probability suggests either extreme confidence in a specific range or minimal trading activity. Comparable July days in 2023 and 2024 saw highs between 78–86°F; the National Weather Service Chicago office publishes extended forecasts roughly ten days ahead, with meaningful refinement occurring 72 hours prior to the target date. Traders implementing automated monitoring should flag the NWS Chicago forecast page and Weather Underground's hourly updates as primary data feeds, since atmospheric conditions in late July depend heavily on upper-level ridge positioning and Great Lakes influence—variables that shift substantially in the final three days.

For programmatic approaches, the key dependency is Weather Underground's historical data lag. Conditional orders should account for a 2–4 hour delay between observation and archive publication. API-based tools monitoring KORD station data will need fallback logic pointing to NOAA's National Centers for Environmental Information if Weather Underground experiences delays, though the market's resolution source is explicitly limited to the former platform.

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

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

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Polymarket Bot UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.