Highest temperature in Chicago on Sep 11, 2026?

📊 Market Summary

🌦️ Highest temperature in Chicago on Sep 11, 2026?

6 options total

🎯 Best Trade

• Action: 80° to 81° — YES @ 72%

• Confidence: 🟡 MEDIUM · Uncertainty: HIGH

• Why:

• The station is already at 80.6°F, so only ~1.4°F of additional heating is needed to reach 82°F — a plausible afternoon outcome that justifies the 26% price.
• GFS raw output of 80.9°F is the warmest model and still below 82°F, meaning the band requires an upside surprise versus every model.
• NWS explicitly forecasts 80°F, not 82°F+, so the settling agency's own number argues against this band being the modal outcome.

📈 Where the Market Stands

Verdicts compare my own read against the market price — 🟢 UNDERPRICED (market has it too low) · 🔴 OVERPRICED (market has it too high). The analysis below is the why.

🔬 9-Pillar Analysis (Meteorological Method)

🌡️ 1. Forecast Consensus

My Vegas Line reads the 80-81°F band as the clear favorite at ~72%, with the NWS point forecast for Midway at 80°F and the station already at 80.6°F — the market's favorite is well-supported by the settling agency's own number.

📊 2. Ensemble Spread

Raw model spread for Sep 11 is 3.3°F (GFS 80.9, ECMWF 77.6, ICON 80.0), which is tight enough that a 2°F band call is defensible, though ECMWF's 77.6°F outlier sits just below the favorite band.

⏳ 3. Forecast Skill Decay

This is a same-day market with the station already at 80.6°F at 19:20Z, so skill decay is minimal — the observation is the dominant signal, not a multi-day forecast.

📈 4. Historical Base Rate

Climatological base rates for Chicago Midway around Sep 11 are not in the intelligence, but the observed 80.6°F and NWS 80°F forecast anchor the distribution firmly in the 80-81°F band.

🔀 5. Model Divergence

If ECMWF's 77.6°F outlier is right, the 80-81°F band dies and 78-79°F becomes live — but that model is the lone dissenter against GFS 80.9 and ICON 80.0.

📍 6. Micro-Climate Bias

Midway (KMDW) is the resolution station, an urban heat-island site that runs warmer than O'Hare; the observed 80.6°F already confirms the warm bias is active today.

🌀 7. Storm Track

Not a tropical/severe weather contract — no storm track applies; the relevant 'track' is the diurnal temperature curve, which has already peaked at 80.6°F.

💰 8. Market Pricing

HIGH - the market is liquid ($76K volume), the NWS point forecast and observed station data both point to the 80-81°F band, and the pricing is consistent with the settling agency's own number.

⚡ 9. Contrarian Check

The main contrarian risk is that the station has already hit 80.6°F and could tick to 82°F+ if afternoon heating continues, which would kill the 80-81°F favorite and pay the 82-83°F band at 26%.

⚠️ Disclaimer: AI can make mistakes. This is not financial advice, and not a meteorological forecast — verify against NWS/NOAA and current model output before placing any trades.