I don't know much about lawns , I just posted a plea for help earlier today.
But I used Scotts turf builder weed & feed at first before I had issues with my septic killing my lawn , & it seemed to work great to kill the weeds & green up the existing grass. They sell a spray on & granule.I used the spray on first time, then I used an aerator, and then mixed my seed & the granule together when I put it out with a spreader the following spring.
My lawn was looking awesome, until my septic system broke & fried my lawn. Have not been able to get it back yet.
Good luck to ya, maybe some of these guys on here might have better advice.

If you want to renovate (kill everything and start over with seed) then you should wait till late summer. If it was me, this is what I would do. Get your soil tested by a reputable lab. I recommend Logan Labs, get the standard test, $20. While you're waiting for the results I would try to kill all the weeds possible. Weed and feed products are NOT recommended. They are a way the fertilzer companies can charge you more for something you don't need. Get Weed B Gone Max and Weed B Gone Clover, Chickweed, and Oxalis killer, the concentrates, not the premixed. Read all labels. Get a tank sprayer. Mix the required amount of both in with the appropriate amount of water, and spray anything that you don't want in your lawn. Meanwhile treat your lawn like you are going to keep it. Frequent applications (monthly) of organic fertilizer like Milorganite, corn meal, soy meal, etc. will raise the organic matter levels in your soil. When the soil tests come back you will add things to improve your soil further. Wisconsin is Kentucky Bluegrass country, unless you don't have a lot of sun. KBG is very cold tolerant unlike perennial rye and tall fescue to an extent. What does the tag say on the bag of grass seed you bought say, i.e. the types of grass in the bag. If it isn't KBG, you might want to think about new seed. Timing is key in seeding grass. I live in CT, my time of seeding is around Sept. 1. I want to say you should be seeding around August 1, which means spraying round up mid July if you are doing one app, July 1 if you are doing 2 apps. Once everything is dead, then mow the dead stuff as low as possible using the bag attachment on your mower. Personally I like to power rake after you mow. It loosens up the soil, and breaks up some of the dead roots. Some people don't like to because they feel like it brings up weed seeds, but you will get some weeds either way, it's your call. After the power rake I manually rake everything smooth. Then I seed at the appropriate rate (don't think more seed is better, it's not). Then I roll the seed with a water filled roller. I like to topdress my seeds, it's not necessary, but I think you get better germination, and your risk of seed wash out is lessened with heavy rain. Then you can roll again since you rented the roller already. You can top this off with shredded straw if you want, again, not necessary, but it can prevent wash out even more, and it will become organic matter in the long run. Then I like to apply a half app of starter fertilizer. Then you water three to four times a day, for 10-15 minutes to keep everything moist, but not soaking wet. Once the grass hits about 3 inches then you can mow it down to 2.

Thanks! I don't like Weed and Feed products, they have a tendency to end up in my flower beds. I'll tell my husband to start using the Milorganite more often. He's got a bottle of Weed B Gone Max but hasn't used it yet this spring since the temperatures have been too cold.

The grass seed is:
50% Kentucky Bluegrass (7 elite varieties)
25% Creeping Red Fescue (1 elite variety)
25% Perennial Ryegrass (2 elite varieties)

I should get a soil test, but I think the soil is fine because my flower garden right next to the lawn has great soil and I've been able to grow anything there. I don't use fertilizer on it either. I think whatever grass it was seeded with originally doesn't appreciate hot sun and not much watering since the grass in a shaded spot nearby does much better.

"I should get a soil test, but I think the soil is fine because my flower garden right next to the lawn has great soil and I've been able to grow anything there. I don't use fertilizer on it either."

Growing grass is not the same thing as growing flowers. You don't cut flowers every week during the growing season. Also grass is millions of plants, they deplete the soil much faster than a typical flower garden. A lot of people think their soil is fine, but in reality, it isn't. If you want a nice lawn, you can't do that with poor soil.

"I think whatever grass it was seeded with originally doesn't appreciate hot sun and not much watering since the grass in a shaded spot nearby does much better."

Most grass likes a lot of sun, and requires regular water, one inch per week is the rule of thumb, but that varies depending on soil type, weather, and other factors. If the grass in full sun is struggling, it probably means it is lacking adequate water.

The grass seed you listed should list the varieties of grass, instead of saying "elite variety". What you are describing is typically called a northern mix. It's OK if you just want an average lawn, but personally I don't think it's an ideal solution.

Last year we had record rainfall and most weeks it was over an inch of rain. The grass doesn't get watered as I don't appreciate the grass and prefer to conserve water. I don't need a perfect lawn, but this is the front yard and I'd like to have something that looks more like lawn than the current weedy carpet.

I chose the grass seed as it was developed for the parks in Madison and I figured it would be tough enough to withstand my lack of watering. I can check the bag to see if it lists the exact varieties, the short list was off their website. Would you recommend something else that would be more able to handle occasional dry spells?

Also, from a quick google search I found the UW extension had this to say about the seed: Some of the "common" cultivars of Kentucky bluegrass are Delta, Kenblue, S 21, Alene, Newport, and Park (not to be confused with "Madison Parks" which is a desirable mixture packaged by Olds Seed Company of Madison).

If you are not going to water it when it looks dry, then you are going to be facing this issue forever. Most of us prefer to get the lawn set up and maintain it with water, mowing, and fertilizing rather than setting it up year after year and letting it die.