Q.Early warm weather and crabgrass germination
We have had an early warm spell followed by a hard freeze, in the teens several mornings. Will the freeze kill any crabgrass that has germinated and sprouted? Should I wait until soil temps warm again for crabgrass preventer or apply ASAP?

The frost is not likely going to kill the Crabgrass.
Spring is a good time to apply selective herbicides.
Check with your local County Extension Office for advise on weed control in your region.
Here are some links with more information.
https://www.gardeningknowhow.com/extension-search/
https://www.gardeningknowhow.com/plant-problems/weeds/crabgrass-control.htm