Hi James, thanks for the question.

The temperature you should be looking for is most likely the average for about four days at a specific depth (for crabgrass 1 or 2 inches).  Different models will yield slightly different results.  An easier way to get the timing right is to use the degree day tracker tool (see link below).  This model uses growing degree days to predict the appropriate timing for the preemergent.  All you have to do is select the Crabgrass PRE model and put in your zip code. Currently your area is at ~170 Degree Days (Base 32).  Looks like it will be more than a week before it is time. Another sign of when to put down the crabgrass preemergent is when forsythias bloom. Check out the following links:

GDD Tracker 4.0 - Turf Pest Management Tracking and Alerts with Growing Degree Day Models for Michigan, Illinois, Indiana and Ohio - Project initiated by Michigan State University (msu.edu)

Timing crabgrass preemergence applications in spring - Turf (msu.edu)

When Will Crabgrass Germinate? | Purdue University Turfgrass Science at Purdue University

I hope this is helpful.