Highest temperature in Chicago on August 9?

Platform comparison

Market context

Chicago O’Hare’s highest reading on 9 August will be settled off the Weather Underground daily observations table, and the crowd is effectively treating the **84–85°F** band as a lock, with the market showing **100%** implied probability there. That makes the current favourite clear and leaves the rest of the book priced as near-total underdogs, so the only real value question is whether the reported maximum ever printed outside that bin before the window closed. [3]

Historically, early August in Chicago often lands in the low-to-mid 80s, which makes an 84–85°F outcome look broadly in line with seasonal norms rather than an extreme. AccuWeather’s monthly Chicago page shows 9 August around **87°F/71°F** for the day, while the National Weather Service climate report for O’Hare is the kind of source used to frame realised daily maxima against normal summer warmth. In handicapper terms, the consensus is overwhelmingly with the favourite, and any contrarian angle would need a late observation or reporting quirk rather than a genuine weather upset. [1][2][4]

The key catalyst for traders is not a forecast change now, but whether the final O’Hare observation for the settlement day was already locked in before any later corrections or additional datapoints appeared, since the market rules give primacy to the daily observations table and allow revisions only until the first datapoint for the following date is published. That means the practical watchpoint is the timing of the final Weather Underground update rather than new model runs, with any late-day heat spike or correction mainly relevant if it altered the recorded high before the cutoff. [3][5]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Chicago on August 9? 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

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.

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.

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Who Will Win 2026 trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.