90% — Rain in Chicago in Apr 2026
Leader: Above 1 inch at 90% · Kalshi 90% · 4 contracts · $4K volume · medium confidence
Updated 2026-05-09 07:22:03 UTC

Tracks the leading outcome in a winner-take-all prediction market set with 4 outcomes.

Why this matters:
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.

Key factors:
- 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

Contracts:
- Rain in Chicago in May 2026?: Above 1 inch — 90¢ Kalshi $395 (weight 10%)
- Rain in Chicago in May 2026?: Above 2 inches — 62¢ Kalshi $3K (weight 69%)
- Rain in Chicago in May 2026?: Above 3 inches — 39¢ Kalshi $416 (weight 11%)
- Rain in Chicago in May 2026?: Above 4 inches — 15¢ Kalshi $377 (weight 10%)

Cite as: "90% per prediction markets (SimpleFunctions, May 2026)"
Canonical: https://simplefunctions.dev/answer/rainchim
Full data: https://simplefunctions.dev/api/public/query?q=Rain%20in%20Chicago%20in%20Apr%202026
Provider: SimpleFunctions — https://simplefunctions.dev