Certified GKH Gardening Expert
You can start whenever your soil is workable. Be sure the soil is dry, though. If you are clearing an area of weeds before you start to prepare soil for garden plants, the product instructions will tell you how long to wait before planting.
For an organic control, boiling water will kill weeds (and anything else nearby) if you have an area you want to completely rid of weeds and undesirable plants.
If you are growing vegetables, the seed packet will tell you when to start for your planting zone, which is 6b.
For transplants, it depends on whether you are growing cool season or warm season veggies.