If you're seeding grasses that are truly native to your area they should germinate with whatever winter weather you have, because, well, it's native to your climate. I find that a lot of seeds aren't well-marked regarding what is actually native to your state, or even county level (grasses native in Corpus Christi may not be native in Lubbock), and whether they need cold stratification.

I would try to find a trusted source (both for seeds and info) for natives for your county, or at least state. Your extension service is often a good place to start. I always trust that more than what's on a seed packet, unless the seed source is a known organization for reliable info (otherwise, it's likely more market-driven than native flora science).