Late Summer and early Fall is the best time to seed your yard in Minnesota, generally around Labor Day or the few weeks that follow because the weather is starting to cool down and there is a nice dew present most mornings. Another big reason is because the Spring pre-emergents have had a chance to work their way out of the soil.
As a homeowner, there are a couple of important steps you’ll need to take to prep your lawn. The first is eliminating any remaining summer weeds (oxalis, spurge, purslane, quackgrass or crabgrass). The first three can usually be taken care of with a selective herbicide that contains 2-4d and crabgrass with a selective post-emergent for annual grasses. Quackgrass, however, will need to either be pulled by hand or carefully taken care of with a non-selective like Round-Up. When using any of these products, make sure they work out of the soil within 2 weeks, otherwise you run the risk of putting down seed that will never germinate.
The second step is prepping your yard to create the best seed-to-soil contact. In patchy lawns, putting down top soil with seed is a great way to fill in bare areas and in healthy yards, dethatching or aerating first will greatly decrease the thatch and increase the percentage of seed germination.
After the lawn has been dethatched or aerated, then you can put down seed. For Minnesota, Kentucky Bluegrass, fine Fescue and a perennial Ryegrass mix will suit most lawns, however if make sure to use a dense shade mix if your lawn calls for it. Red Fescue should be present in the mix for shaded lawns since it only requires a few hours of light per day. And a finally note on grass seed: pick up a quality seed that does not contain much filler. Also, stay away from the easy-seed and patching mixes because they are only meant to fill in small spaces such as pet spots.