It's usually a stress response at normal mowing heights, so the sudden temp increase is probably the culprit. Nothing to worry about.

@dchall_san_antonio - Thanks for the information. I have fiskars manual mower which only goes as low as 1 in. We just had a newborn coming into our family and with another toddler, I was getting overwhelmed mowing twice a week. So I thought it will be better to mow one step higher if I was going to mow once a week. I didn't know I should water every 5 days when temps in the 100s. I do have some dry dead patches from being drought while we were gone vacation last week. Temps were around 107 for 5 ~ 7 days and I wasn't here to turn on the sprinkler manually. The sprinklers are set to water only on wed because of the water regulation. But I will know next time when it gets very hot (over 100s) I will water 5 days interval. I guess only thing I am missing is to mow 2 times a week at 1 inch. I couldn't afford to buy gas reel mower and I thought fiskars manual mower would have been nice upgrade from craftsman gas mower. But anyway, seems like it is not something I need to treat or anything like that. I guess I will try to change my mowing frequency.
@reeljake - Thanks for the information. Nobody around me mows themselves. They all have lawn service, which comes once every week. They mow very short with their gas reel mower. But no one has seed head coming out like I do. So I was just packing and researching online. If they will not harm my grass, then I guess I will just stop worry about them.

The Fiskars is a good machine, mine lasted about 3 years before the chain stretched & started jumping. I only mow every seventh day, but with Bermuda you could literally mow every day without hurting it. The seed heads should go away in a week or so.

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

I have these seed heads covering about 50% of the yard. Glad everyone responded to this thread- it was really helpful.