CHICAGO — The latest forecast data has backed off on the chance of showers for Saturday, October 31. Much of Halloween may end up dry across northern Illinois, southern Wisconsin, and northwest Indiana. Only light showers are possible at times. Rain totals in most areas are expected to stay well under a quarter inch.
Dry Air Is Blocking the Rain
The main reason for the change is how dry the lower atmosphere has been after a long dry stretch. When rain falls from higher clouds, it has to pass through that dry air first. Much of it may evaporate before reaching the ground.
This process is called top-down saturation, where the air has to moisten from the top down before rain can reach the surface. With air this dry, that may struggle to happen. That means more clouds than actual rain for many neighborhoods.
Light Totals Across the Chicago Area
High-resolution model data through midday Sunday shows only light, scattered rain across the region. Most spots near Chicago and northwest Indiana show totals of 0.01 to 0.05 inches. Many areas may see just a trace or nothing at all.
A few heavier pockets show up west and southwest of the city, with totals around 0.12 to 0.13 inches in spots. Areas along the Illinois-Wisconsin border show isolated amounts near 0.23 inches. These are small, scattered patches rather than widespread rain.
Wisconsin and Michigan See Spotty Showers
In southern Wisconsin, a few bands of light rain are shown north of the state line near Milwaukee. Totals there mostly stay between 0.04 and 0.13 inches. Some spots may stay completely dry…