October in Chicago is the wrong time to plant grass seed. Kentucky bluegrass is used in northern Illinois, according to the University of Illinois. This specific grass seed takes 20 to 30 days to germinate, which even if the seed is planted on October 1, the seed would not germinate until the last week or so in October. Late October is when the soil temperatures have cooled, which is when grass starts to go dormant.
According to Weather by the Day, Chicago has little precipitation on the average. The average precipitation is 2.71 inches of rain and 0.4 inches of snow. Grass seed needs water or rain, but not snow to germinate. In October, precipitation can be rain or snow.
According to Chicago Botanical Garden, grass seed should be sown from mid-August to the end of the August. Soil should be cultivated down a few inches and starter fertilizer needs to be used.