Highest temperature in Chicago on August 9?

Platform comparison

Market context

Chicago’s **highest temperature** on 9 August is trading as a near lock, with the crowd implying **0% YES**, which usually means the market is pricing an outcome it regards as effectively certain. In handicapper terms, that makes the favourite the 84–85°F band, with the underdog side only viable if a late-day warm surge or a reporting quirk pushes the day’s maximum out of the expected range. Chicago’s August climatology supports that favourite: the National Weather Service gives a normal high of **83.3°F** for 9 August, while historical climate pages put the date’s average high in the low 80s, with the all-time record much higher but far removed from the base case.[3][8]

For context, Weather Underground’s Chicago history page shows recent daily highs around the mid-80s, including **85°F** and **84°F** entries in the sample shown, which lines up with the market’s consensus band rather than suggesting upside volatility.[15] Extreme Weather Watch also lists the August 9 average high at **83.2°F**, reinforcing that the centre of gravity for this date is a low-to-mid-80s reading, not a breakout heat event.[8] The value question is therefore not whether Chicago gets hot in an abstract sense, but whether the observed high lands just inside or just outside the tight bin the market is concentrating on.

Traders should watch the actual **Daily Observations** table at Weather Underground, because the contract resolves off that source rather than the summary high/low display. The key catalyst is not a scheduled announcement but the timing of the final observation for the day: the market’s own rules say revisions count until the first datapoint for the following date is published, after which changes are ignored. In practice, that means the only meaningful contrarian angle is a late data update or an observation-time artefact, rather than a weather surprise; absent that, the consensus favourite remains strongly supported by the seasonal pattern and recent Chicago warmth.[6][15]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in Chicago on August 9? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Who Will Win, which mirrors the Polymarket order book at 0% fees.

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.

UK Frequently Asked Questions

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.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.