Normally, core aeration would be done with the fall overseeding. Aeration stresses the root zone and you do it when the grass has the best chance of recovery, which for cool season grasses is fall or spring. Even when watering, the stress of summer heat could be too much and your grass will wilt and die.

Depending on your temperatures and the herbicide, that may not have been the best choice either.

Are you planning your overseeding now? Is there a reason to do it now?

I was going to seed relatively soon.

There's no particular reason to do it now besides "I've got time."

I can put the project off until sometime in September if it's the right thing to do.

Since it is not an exact science and technically you can seed at any time, you want the most favorable conditions when you seed.

What is your location and what do you intend to seed?

What herbicide did you use and what where its instructions about seeding?

I did mine in the middle of July..I live in Alabama and have Tifton Bermuda..It stressed it a lil, now it is fine..I did apply fertilizer right after..

I'm in a Chicago suburb. I planned to use Scott's premium sun/shade blend. I used a Spectracide herbacide. There were no instructions about seeding.

Alleviating compaction is one of the best practices you can do for turf. Core aeration can be done anytime the turf is actively growing.

And in Chicago, you should be fine. Watch the forecast, you want the weatherman to say 'well, it's going to be mild for the next few days'......then get to work.

If the weatherman says 'for the next few days, it's going to be hotter than normal, and no rain for a week'...then wait. Just less than a week.

I think I can count on 1 hand the number of days we've had above 90 degrees. It's humid, but it's a pretty mild summer.

Not sure the herbicide is working well, though. I used the hook-it-to-the-hose-and-spray-it-on type. Only a small percentage of the weeds are showing wilt.

Use the Smith and Wesson method. You've seen that sign, behind store counters....."Tresspassers Will Be Shot. Survivors Will Be Shot Again".....

Give 'em another shot. Seven days after the first is just about perfect.

Yeah, I think that's a good plan. I'll see how it looks over the next few days.

i live in Pa. can I aerate and overseed now? Aug11 2023

Did you read all the replies above? The clues are up there.

Generally you should wait until the summer heat breaks. Philes weather comments above are very helpful.

What you can do now is spray the yard with shampoo at a rate of 3 ounces per 1,000 square feet. I'm not sure much was known or shared about the use of surfactants on turf 15 years ago when this topic was started. Today golf courses use a lot of expensive surfactants to soften their soil. You can do the same thing at home with any clear shampoo. Clear means you can see through it - no conditioners. Dollar Tree shampoos are fine. Apply with a hose end sprayer. If you have 2,000 square feet to cover, put 6 (or more) ounces of shampoo in the tank, fill the rest of the way with water (slowly so it doesn't foam over), and start spraying on any setting. Try to evenly cover the entire yard. Then irrigate or rain on it about an inch to carry the shampoo down deeper into the soil. One inch of irrigation usually takes hours, so this isn't a hand watering situation.

Before you spray or aerate, try the screwdriver test for soil 'softness'. Stick a screwdriver into the soil and make a mental note of how hard it is to penetrate and how far the screwdriver goes. Do this when it is dry and when it has been irrigated or rained upon. Then try the test again 3 weeks after you spray or aerate. What you should find is the screwdriver will penetrate much better after spraying shampoo and likely no change after you aerate.

Here is an image from the Wolfram Alpha website showing the climate in Altoona, PA.

July and August are the hot months. Temps begin to break in September. I'd wait a couple weeks and then start listening to the weatherman as Philes suggests.