Smooth crabgrass (Digitaria ischaemum) is the most common summer annual grass problem in managed turf. It is estimated that 90% of the crabgrass in Michigan lawns is smooth crabgrass. Smooth crabgrass lacks the hairs of large crabgrass (Digitaria sanguinalis) and can be identified by its light green appearance and swollen, zig-zag nodes. Crabgrass is a summer annual that re-establishes from seed every spring.  The best time to stop crabgrass is by applying a crabgrass pre-emergent control in the spring and watering it in at the time the forsythia blooms (which is just before the crabgrass seed germinates).

Since it's too late to do that now applying a post-emergent to kill existing plants before they seed or mechanical removal are options to consider.  

I have attached links to several university articles on crabgrass control (both pre-emergent and post-emergent).  First, use the post-emergent information now to kill much existing crabgrass before it goes to seed late this summer.  Next, use the pre-emergent info next spring to prevent crabgrass germination next year.  Thereafter only use the pre-emergent control in the spring to control existing seed that may germinate in later years.

http://www.msuturfweeds.net/details/_/smooth_crabgrass_49/

https://turf.purdue.edu/smooth-crabgrass/?cat=106

https://plantscience.psu.edu/outreach/plant-id/grasses/crabgrass

https://njaes.rutgers.edu/fs1309/

https://apps.extension.umn.edu/garden/diagnose/weed/grass/smoothcrabgrass.html

Maintaining a healthy lawn (fertilizing, mowing high, etc.) will also help reduce crabgrass establishment.  See the following:

Home Lawns | MSU Extension

Smart Lawns Tip Sheets-MSU

Lawn Maintenance Calendar-MSU

Lawn Mgmt. thru the Seasons-PSU

Why Mow High-MSU