Lavender Thyme Hardiness

What zone is lavender thyme hardiness? I'm in zone 4b, can it stay out over the winter?

The hardiness of lavender thyme is not well established. Presently, we are rating it as hardy to zone 5 and up. It may be hardy in zone 4 but we have no reports on file to verify that.
If you choose to leave the plant outdoors this winter you can improve the chances of it's surviving by applying a mulch in late fall before the first permanent snow fall; in our area that is usually early to mid December. It also helps if the plant is in well-drained soil and on a bit of a slope so water can drain away easily. Most thymes do not thrive in soggy wet soils, especially over winter.