Dave’s Garden has a great tool you can use to enter your zip code and receive your area’s last/first frost dates.
Not only that, but it will provide local “detailed station data” highlighting the percentage of likelihood of receiving frost at particular dates in your immediate area. The result summary will also tell you when you are virtually guaranteed to/not to receive frost. For example, a search for Round Rock, Texas came up with the following summary:
With that information in mind, you can sow seeds indoors according to the seed packet directions and have them ready to go when Mother Nature is ready!