All data sources are in general agreement that a significant rain storm is heading to Chicago. A few showers may arrive Tuesday night, but widespread, areawide rain occurs mainly from Wednesday afternoon through Thursday afternoon. Best estimate now is that we can expect at least an inch of rain. Chicago has received only 53 percent of its normal rainfall since August 1 (5.79 inches versus the normal of 10.95 inches), so we need the rain, but the timing is unfortunate because Thursday is Halloween. Only 35 percent of past Halloweens have had measurable precipitation.
A vigorous low pressure system, moving northeast from the panhandle area of Oklahoma and Texas Tuesday morning to Lake Superior Thursday afternoon, remains well to the west of Illinois, keeping Chicago in the mild eastern section of the weather system.