Highest temperature in Chicago on August 9?

Platform comparison

Market context

Chicago’s temperature on 9 August is typically in the low 80s Fahrenheit, with the National Weather Service putting the normal high at 83.3°F and Weather Underground’s Chicago history page showing a high of 85°F for the date against a historic average near 84°F. That makes a mid-80s outcome the baseline rather than an extreme, which helps explain why the Polymarket contract is concentrated in the 84–85°F band while the crowd-implied chance of a different bucket is minimal.[3][15][1]

For comparison, Chicago’s August 9 record high is 97°F in the long-run data cited by ExtremeWeatherWatch, but that is a far warmer tail than the recent climatology. The market is also resolving off Weather Underground’s Daily Observations table for O’Hare, not the summary “Day High & Low” figure, so traders should focus on the final observed hourly maximum and any later revision before the first datapoint for the next date is published.[7][15][1] On exchange mechanics, Polymarket prices directly as an implied probability, while Kalshi, Betfair and Smarkets typically quote decimal-style prices or odds equivalents, so the same weather view can look different even before fees; access and KYC also vary, with regulated books usually stricter on residency and identity checks than crypto-native venues.[1]

The main catalyst is the actual observed temperature path through the day and whether convection, cloud cover or a late-afternoon front caps the high below the consensus. Recent Chicago forecasts pointed to a humid, partly cloudy setup with thunderstorms possible, which can suppress the daily maximum if they arrive early enough, while a dry, sunny run-up would favour the upper-80s outcome; AccuWeather’s recent Chicago outlook also showed an 87/70-style day, close to the climatological band rather than a heat-spike scenario.[13][6] Because the contract settles on the highest recorded observation within the window, any late update to the hourly table matters more than headline forecast graphics, and that timing nuance is where books such as Betfair or Smarkets may diverge from Polymarket’s straight probability view once commissions are included.[1][15]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in Chicago on August 9? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi Alternative, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). On-chain settlement clears in minutes — the fastest payout path of the four.

FAQ

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Kalshi Alternative has a different geo footprint and routes to Polymarket's order book at 0% fees.