Is this Purple Archangel
You got the extension office right here! It is red dead nettle, (lamium pupurium) a spring weed. It disappears as soon as the weather heats up.
I have never heard of purple archangel, but it could be a common name. It is a very common weed here in MO, but not worrisome, because it only appears for a short time. There are also some cultivated varieties that are more persistent.