Highest temperature in Chicago on August 9?

Platform comparison

Market context

Chicago’s **highest temperature** on 9 August is the key observation for this contract, measured at O’Hare and resolved from Weather Underground’s Daily Observations rather than any headline summary. The market is already pricing an **84–85°F** result at 100%, which is broadly in line with the day’s climatology: Chicago O’Hare’s normal maximum for 9 August is about **83°F**, and recent AccuWeather and National Weather Service reference points also cluster the early-August range in the low-to-mid 80s.[1][2][3][11]

That pricing leaves little room for disagreement, but it also shows how tightly this market can converge once the forecast is near the seasonal norm. Historical Chicago August 9 normals sit around **83.2–83.3°F**, so a bin centred on the mid-80s is the most natural landing zone absent a cold front or late-day convection.[11][13] By contrast, a hotter outcome such as **86–87°F** would usually require stronger southerly flow and clearer, less humid conditions than the long-run average, while anything below the low 80s would typically need cloud cover or rain interference.[1][11]

For traders, the main catalyst is the final O’Hare reading sequence on the resolution day, not the broader Chicago forecast. The market’s outcome is determined by the highest value recorded before the next day’s first datapoint appears on Weather Underground, so late-afternoon warmth, brief spikes, or any post-peak cooling pattern matter less than the exact top print.[3] Cross-platform comparison is notably one-sided here: Polymarket’s own contract is already at a near-certain **84–85°F** bin, with no meaningful published sportsbook-style contrast visible in the supplied sources, so the main risk is not market disagreement but a late weather revision or observation timing issue.[3][4]

Sources: 1 · 2 · 3 · 4 · 5

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 PolyGram, which mirrors the Polymarket order book directly.

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

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.

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.

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.