# Rain in Chicago in Apr 2026

> Above 1 inch leads at 90%, runner-up 62% across 4 winner-take-all outcomes — refreshed 1 min ago.

URL: https://simplefunctions.dev/odds/rainchim
Updated: 2026-05-09T07:20:22.797Z
Category: general
Status: active
Closes: 2026-06-01

## Headline

- Leader: Above 1 inch at 90%
- Runner-up: Above 2 inches at 62%
- Outcomes: 4 (winner-take-all)
- Venue: Kalshi (4 contracts)
- 24h volume: $4K

## Bound contracts (4)

| Outcome | Price | 24h | Volume | Venue | Slug |
|---|---|---|---|---|---|
| Above 1 inch | 90¢ | −1pp | $395 | kalshi | /markets/rain-in-chicago-in-may-2026-above-1-inch-kalshi-kxrainchim-26may-1 |
| Above 2 inches | 62¢ | −8pp | $3K | kalshi | /markets/rain-in-chicago-in-may-2026-above-2-inches-kalshi-kxrainchim-26may-2 |
| Above 3 inches | 39¢ | −2pp | $416 | kalshi | /markets/rain-in-chicago-in-may-2026-above-3-inches-kalshi-kxrainchim-26may-3 |
| Above 4 inches | 15¢ | −5pp | $377 | kalshi | /markets/rain-in-chicago-in-may-2026-above-4-inches-kalshi-kxrainchim-26may-4 |

## 30-day trajectory

| Day | Above 1 inch | Above 2 inches | Above 3 inches |
|---|---|---|---|
| 2026-05-01 | 73 | 66 | 55 |
| 2026-05-02 | 98 | — | 68 |
| 2026-05-08 | 91 | 71 | 42 |
| 2026-05-09 | — | 63 | 40 |

_7 days of price history captured. Each row is the daily mean of intraday 5-min captures._

## What moved the line

- 2026-05-02 · Above 1 inch +25pp 73→98¢ · kalshi
- 2026-05-03 · Above 2 inches +22pp 66→88¢ · kalshi
- 2026-05-03 · Above 3 inches −15pp 68→53¢ · kalshi
- 2026-05-02 · Above 3 inches +13pp 55→68¢ · kalshi
- 2026-05-08 · Above 4 inches −13pp 31→18¢ · kalshi

## 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.

### 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

## Methodology

Headline is the **leader's price**, not an arithmetic mean — averaging disjoint winner-take-all outcomes is meaningless. Per-outcome prices come from the venue's last-traded mid; cross-venue values are simple means across contracts on each venue.

## How to use this data

- HTML: https://simplefunctions.dev/odds/rainchim
- JSON: https://simplefunctions.dev/api/public/odds?slug=rainchim

## License

CC-BY-4.0. Attribute "SimpleFunctions" with a link to https://simplefunctions.dev. See https://simplefunctions.dev/legal for terms.