Michigan has hardiness zones 3 through 6.*
Here's a planting calendar for hardiness zone 5 you can use as a guide.
For the sprouting of seeds it would be the soil temps that would determine when they would sprout.* If the seeds are in the ground for 3 weeks or more they probably won't sprout.* Your seed packet should tell you how long it takes for the seeds to sprout (germinate).
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.