All I can think of is clover.
It's rough when you live downwind of folks who don't care to get rid of weeds but all you can do is add many spot treatments and couple times a year full weed treatments to your list of yard chores. Sorry

Thanks, but no it isn't clover, the seed heads are white and airy and fluffy and light enough to float on the breeze. How often can you do a full weed treatment , are there set times?

Is it the one where the foliage looks like Phlox subulata? If so, that is an awful weed, but I don't know that I ever learned the name. Now when I see it, I pull it right away. There was one guy in my neighbor whose lawn was taken over and when it went to seed, it looked like snow, just like you said.

What your neighbor has is Poa Annua or Annual Bluegrass. It is an annual that germinates in the fall and dies around May, that is why it has gone to seed. There are no selective controls for this as it is a type of grass. You can put out pre-emergent in Sept to stop the germination but be careful if you are also planning to aerate and seed as the pre-emergent will stop all grass seed from germinating.

No, don't think it is annual blue grass either. The seed heads actually are rounded sort of and have fluffy white seeds. Really reminds you of dandelion , sturdy plant/weed. Doesnt seem to have leaves just short whorls around a stem., then a seed head. darn camera. must get pic.

Could this be it

Annual Trampweed or facelis

That's the one I was thinking about!

Here is a link that might be useful: Facelis retusa

That's it ! ! Thanks for all the help ! Now I know how to prepare for next year. Thanks again.