96% — Rain in Chicago in Apr 2026 Leader: Above 3 inches at 96% · Kalshi 96% · 7 contracts · $10K volume · medium confidence Updated 2026-08-10 12:59:35 UTC Tracks the leading outcome in a winner-take-all prediction market set with 7 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 Aug 2026?: Above 3 inches — 96¢ Kalshi $4K (weight 38%) - Rain in Chicago in Aug 2026?: Above 4 inches — 92¢ Kalshi $3K (weight 32%) - Rain in Chicago in Aug 2026?: Above 5 inches — 82¢ Kalshi $280 (weight 3%) - Rain in Chicago in Aug 2026?: Above 6 inches — 62¢ Kalshi $1K (weight 12%) - Rain in Chicago in Aug 2026?: Above 7 inches — 37¢ Kalshi $481 (weight 5%) - Rain in Chicago in Aug 2026?: Above 8 inches — 16¢ Kalshi $408 (weight 4%) - Rain in Chicago in Aug 2026?: Above 9 inches — 6¢ Kalshi $539 (weight 6%) --- ## Methodology SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours. ## SF Signal - SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration. - No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only. --- *Last verified: 2026-08-10T12:20:51.793Z* By SimpleFunctions — https://simplefunctions.dev/ Cite as: "96% per prediction markets (SimpleFunctions, August 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