When to transplant outside

Like the title says when is a good time to transplant outside in Michigan. I am on the west side about in the middle. Oceana County Michigan.

Get one of those handgun temperature thingies, the ones that shoot out a beam of light and give you a temp. Your soil should be 60F or more. If you go too early, you can stunt the plant. If the forecast is cloudy and cool, might want to hold off - gotta play it by ear. Also watch night time temps. You want consistent lows in the 50s. Lows in the 40s is too cold. It somewhat depends on the size of your seedlings as well. Larger seedlings are more robust. I am in zone 4B in MN, and we are very close to planting, within a few days. If it wasn't so wet, it might even be okay now. I measured soil temp, today at 58F with nighttime temps in the low 50s, and sunny weather forecast. Still feels a little early to me, though, but not by much.

Also important that there is at least 14 hrs of light, less can cause them to flower.