I live in Waukegan and it seems that rain frequently misses the area, but points south receive a good soaking. What is physically stopping rain from hitting here?
Rain occasionally hits some areas especially hard and misses other areas, but over the long haul, it all averages out. Precipitation may have been missing Waukegan recently, or at least rain falling there has been lighter than in areas farther south, but there have been other times when the northern suburbs have repeatedly received more rain than areas to the south. Averaged over a long enough period of time (weeks, several months, or even a few years), precipitation occurs everywhere in the Chicago area at the same rate, with certain exceptions (lake effect snow, for example).