My last graft of the year is tomorrow, with last cells going out to mating nucs 10 days later. Our Goldenrod flow is usually August 15-early September. Nucs made by first week of August usually winter well, although maybe with somewhat smaller clusters.
If you're going to raise some cells, you better get to it. If you start a cell builder tomorrow using the method I use, your graft will be on July 29, and cells ready on August 8. Queens won't be mated and laying until about the 24th of August. Then if you're going to winter nucs with them, that seems kind of late for me here in Vermont.