Its hard to tell from the pic but the blades
that are still green look like they have a
fungus of some kind. Blight, red thread, or
leaf spots I couldn't say from the photo.
Someone else might be able to diagnose it
more exactly. If it were my yard I'd rake the
brown out, spray some baking soda solution on
it and re-seed if its not too hot and if you're
in Ontario (?) then its probably not.

Looks like some spots in my yard. I'm currently battling dollar spot fungus. Its hard to tel without a close up but my guess is a fungus of some kind.

Fungus!! Who'da thought?
Don't you need damp conditions for fungus to thrive? yes, we've had rain, but there are far damper corners of the garden that do NOT have fungus. In fact, that's where I grow moss among the grass and it's all very lush :)
These brown blades are all throughout the sunny part of the lawn (which is unfortunately most of it). It would mean that this fungus spread over the area in less than a week.

Another theory: could these brown ones be the ones that came up when I overseeded and they, being a different type of grass, just don't cut it in this location?
Hmm, I wonder if I accidentally used my 'shade mix' that I bought for the front lawn. Possible?

Has it been hot and/or dry lately? Perennial Rye in many mixes tend to brown out under those conditions. I would especially consider this if the yellowed blades are diffuse throughout.

This is driving me nuts because I've this before but can't remember what it is.

"could these brown ones be the ones that came up when I overseeded and they, being a different type of grass, just don't cut it in this location?"

It's not probable since the grass you purchased is sold in your area because it is suitable in your area. Grasses that cannot survive the location are not sold in said location.

"Hmm, I wonder if I accidentally used my 'shade mix' that I bought for the front lawn. Possible?"

Also not probable because "shade mix" means those grasses will thrive in shady conditions. Many won't, so some that will were mixed together to form a strong and shade-tolerant sod. It doesn't mean they won't survive sunny or non-shade conditions. I hate to say I've seen shade mixes with ryegrass in them. Really dumb thing to do, but the rule remains theorhetically.

I can't help thinking there is something you forgot to tell us, like you fertilized, when you fertilized, and how much.

Is there anything you forgot to tell us?

What was the pre-m you used?

As others have mentioned, I don't think the spots on the grass should be ignored. Show us closeups so we can see them better.

Thank you for your help! Below is another picture, probably as close as I can get with this camera. This coloration seems to be more like something you'd expect after a drought.
The weather here has been pretty crazy these past few weeks. From hot humid temps in the high 80s to nights with frost warnings. We've been getting rain, mostly in the form of downpours, over the past few weeks. Not a lot of long, steady rain.

The pre-emergent I used was Scott's. There was no burning as might be evident by yellow streaks. The CGM I put down was just cast around by hand, and not especially thickly.
The front lawn got the same treatment (i.e. crabgrass) as the back, but it doesn't have this yellowing. Then again, it gets more shade and I used the shade mix there.
The crabgrass treatment appears to be working. So far there is no sign of it in the lawn, but has been sprouting along the edges and untreated areas.
I do have lawn weeds of all descriptions but none except that creeping stuff with the little white flowers is much of a threat (clover, the odd dandelion and plantain, some strawberry-looking stuff, other odds and ends). The new grass is doing the job of crowding a lot of it out. So far.

Because of my garden beds I have lots of turns and corners and so it's easier for me to use a reel mower. I do have an electric rotary but it's a PITA. I do suspect the reel mower blades of being dull - I can't find any place that will sharpen them. I do use the electric when things are really thick and I want to mulch the cuttings as I go.

That's about all the info I have on this lawn. It's new to me and I don't know its history. I do see, even with my untrained eye, a variety of grass types in it.

{{gwi:101898}}

Could be a poorly adapted grass (Perennial Rye or Fine Fescue in full sun).

Chris,

That picture looks less like a fungus to me than
the first one did but I'd still recommend the same
thing. Rake it and re-seed. I can't imagine that
your soil temp is much above 60 that far north so
its not at all too late to re-seed for this season.
As far as the mower blade is concered the blades of
grass do look a little brown at the top but not
terribly jagged.

I'm going to have to give you two posts, for two links, as the garden web appears to only let me post one at a time.

Necrotic ring spot appears to be one possibility. Here's a link to it. But keep hitting the "next" button, at the bottom. It will take you to more pics and symptoms.

Here is a link that might be useful: Necrotic Ring Spot

Here's the main page, or table of contents, to Penn State's turfgrass articles. The one you want is "Managing Turfgrass Diseases" but the rest of the publications might be of interest as well.

Here is a link that might be useful: Penn States Turfgrass Publications

Philes, for future reference, you can post more than one link if you add the html yourself. To add a link, do something like this:

<a href="some.link.here/whatever.html">text to display</a>

That will link to some.link.here/whatever.html and display "text to display" on the page.

many thanks, BP. How's yours looking, as we come toward the 4th of July?

My own theory, soon to be picked up by a major studio, is that one's lawn will never look better than it looks on the 4th of July.

My lawn looks fine right now because we had more than 2.5 inches of rain Wed and Thu of this week (average June rainfall is .77 inches).

July 4 may be the best time for lawns in MI, but not in UT. My lawn looks best from September through May, since those are the only months we average more than an inch of precipitation. I usually hit the lawn with a high nitrogen fertilizer in late fall, after the top growth has stopped but while the grass is still green. That way, the grass stays green all winter (although sometimes I have to take that on faith until the snow melts).