I think you're killing your lawn with kindness. I assume you have a fescue or Kentucky bluegrass lawn (or mix). It sounds like you are watering far too often. Once you get temperatures into the 90s every day, then you should be watering once per week. With temps in the 80s you should be watering once every 2 weeks. Why? Couple of reasons. One is that crabgrass seed must have continual soil moisture for several days to germinate. Without that, it cannot germinate. If you water once, deeply, the surface of the soil will become dry long before the root zone dries out. Just doing that prevents crabgrass. PREVENTS! You don't need a preemergent if you just do that. However, sometimes Mother Nature steps in to ensure there is continual moisture. That is when you might need a preemerge. The second reason is that if you water every day, the soil dries out down below and the roots only grow at the very surface. If you miss a day of watering, the soil surface can dry out and kill the grass. But if you water deeply, the grass roots will penetrate as deep as they need to to find that moisture. Growing deep roots takes time if all you have is short roots, so don't try to go cold turkey with your watering plan. You should wean the grass off of the "day and night" watering until you are watering a full inch, once per week in the summer heat. Doing that will stop most new weeds. It will not kill out the current crop of crabgrass. There are some herbicides that apparently work. I'm an organic kind of guy and have not had appreciable weed problem in a long time, so I don't keep up with herbicides. Someone else will come along and help with that. What I would do is suffer along through the summer. Then in early September (in your area) I would kill off the crabgrass, rake it up, reseed, and try to establish as dense a turf as you can before next spring. Crabgrass is an annual plant so it has to come back from seed. If you are watering correctly next year, then you can have all the seed you want but it won't sprout on the dry soil surface. Crabgrass is lighter color than most turf grasses. That might be what you see. Otherwise, have you fertilized? Usually that evens things out. If you want an absolutely hassle free fertilizer, use organic anything. My favorite is alfalfa pellets (rabbit chow). Get it at your feed store in a 50-pound bag for about $15. Apply at 20 pounds per 1,000 square feet. Since it comes in a plain bag, there are no directions to read and hassle with. Just apply at 20 per 1,000 and let Nature take Her course. In 3 weeks the grass will become much greener, more dense, and will be growing slightly faster. Here is a demonstration picture taken by mrmumbles a couple years ago. Organic is also no hassle because you cannot over apply it. If you double the dose, it just lasts longer. If you apply as much as 80 pounds per 1,000 all at one time, you do run the risk of smothering the grass - not to mention severely denting your lawn care budget.

It might be better to check the soil before watering and if it's still damp, wait a day or two before giving it another drink. ~Something else to consider is if it's sitting on concrete and getting full sun it could be baking it? I'm not sure about the last one but if less water didn't help, I'd try putting where it could get a little shade. Hope I was able to help but someone else might do better! ~~Anyway good luck with your grass... the plumes will be worth the trouble in a few months!!

My first thought was that you were watering every day. Is that what you meant by 30 minutes if it didn't rain? Here's a picture for you to contemplate. The green lawn belongs to morpheuspa, the previous poster. All the rest of the lawns look like yours. All these are the same type of grass. Back when this picture was taken, morph was watering deeply once per week. All the neighbors watered every day. Deeply for you means 2cm all at one time. Place some tuna or cat food cans around your yard and turn on the sprinklers. Time how long it takes to fill all the cans. It takes my sprinkler 8 hours, but yours will probably fill faster. That time will become your normal watering time from now on. The once per week timing was based on the summer heat of Eastern Pennsylvania that summer with temps above 30 C. If your temps are lower than 30, you can probably deep water once every 10 days to 2 weeks. But if you're currently watering daily, you'll have to wean your lawn off of that frequency. Start by doing the tuna can test. Then don't water until the grass starts to look dry. Hopefully that won't be for a few days. Then water deeply again and watch for the grass to turn dry. Hopefully, again, it will be a day or two longer than the previous time. Keep doing that until the lawn is going the week to 2 weeks without watering. Also if you are not mowing at the mower's highest setting, try changing that. All this is to develop deeper roots which bring up moisture and nutrients from deeper in the soil.

It could be annual rye grass that got mixed in and is going to seed