Rain in Chicago in Apr 2026

30-day trend

Analysis

Markets currently assess a 90% probability that Chicago will receive at least 1 inch of rain during May 2026, based on active trading across four rainfall-threshold contracts. This high confidence reflects normal climatological expectations: Chicago receives measurable precipitation on roughly 40% of May days historically, and monthly totals above 1 inch are typical for the month. The probability could move lower if extended high-pressure systems establish dominance over the region, suppressing storm formation. Conversely, it could edge higher if seasonal forecasting models indicate above-normal moisture transport or enhanced frontal activity. Resolution depends entirely on weather observations recorded through May 31, 2026. The spread between contract prices (90¢ for above 1 inch versus 15¢ for above 4 inches) suggests traders view moderate rainfall as likely but substantial accumulation as less probable.

• ›Chicago's historical May precipitation averages 3.7 inches, making at least 1 inch occurrence well above 50% baseline
• ›The contract price decline from 90¢ to 15¢ across increasing thresholds indicates traders assign significantly lower probability to heavy rainfall (>4 inches)
• ›24-hour trading volume concentrates on the 1-inch and 2-inch thresholds ($2,397 and $395 respectively), suggesting market focus on typical versus above-normal outcomes
• ›Seasonal weather pattern shifts in late May can introduce atmospheric instability; early June typically marks more active convection, creating boundary effects near month-end
• ›Daily weather observations through May 31, 2026 constitute the sole resolution mechanism—no intermediate data releases or forecasting updates will alter the final outcome

What moved the line

• Aug 2Above 4 inches↑15pp62→77¢ · Kalshi
• Aug 6Above 3 inches↓14pp91→77¢ · Kalshi
• Aug 1Above 5 inches↑13pp38→51¢ · Kalshi
• Aug 2Above 3 inches↑11pp83→94¢ · Kalshi
• Aug 7Above 3 inches↑10pp77→87¢ · Kalshi

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These markets stopped trading. Last odds and any captured outcome are shown above — full settlement detail lives at the venue.

How we compute these odds