Henbit

Apparently the extra warmth here after a period of not-as-warm has fooled a few plants into growing and blooming at the wrong time, though they look a little pathetic.
This is one. Henbit, or Henbit Deadnettle Mint, is usually a early spring bloomer and a winter annual, but among some of the patches I've been finding there have been one or two and there with a few blooms.
It's pretty obviously a mint, it has a stiffly perfect square stem and a strong smell when crushed. I'm not sure how to describe the smell, it's like a cross between pine and fresh catnip. They only grow between 4 and12 inches high and look quite flimsy with it's skinny stem and large leaves and top-heavy flower head. The stems are a dark purple color for the most part (not to be confused with Purple Deadnettle which has purple leaves as well), and the whole plant grows from a taproot*.
The leaves are opposite and lack petioles on the upper part of the plant. They're deeply incised with a scalloped (and crinkly) look to them. Where the leaves connect to the stem there's a fuzzy looking area that looks like it used to hold flowers.
The flowers are pink to purple and grow in whorls, they are tubular and about 1/4 - 2/3 of an inch long.
Henbit is more likely to be found growing in buffalo grass than the softer bluegass or other soft northern-type grasses. This means it can grow pretty much anywhere down here, but its range reaches up to Canada/Greenland and it has to compete a little more in some of it's range.

If you suspect you've found a mint in Texas, this website is quite nice. It has good descriptions along with photographs of all the species and subspecies.

*Taproot, in simple terms: a single root. Think carrot or dandelion, not tree or clover.