Looks like you are figuring it out. I am just beginning to plant brassicas but I don't have deep freezes. First frost around Thanksgiving and ground never freezes. Hoping for a cool wet spell as the hurricane season ramps up. Dry and hot does not suit brassicas and fall crops at all. Hope to get carrots in soon. Broccoli , cauliflower, cabbage, Napa cabbage, collard plants going in this week along with direct seeded turnip, mustard, rutabaga, pak choi. I will make a second planting of collards turnip, and mustard in October. Spinach sometime later in the month. My time line is very much weather related.

It's always hot here in late Aug but I usually have good success & harvests planting carrot, beet, spinach, collards, and turnip all from seed during a short window of Aug 20-27. Also plant cabbage & broc transplants but have to shade them during the heat of the day until they acclimate after 10 days or so.

Following farmerdill's recommendations he gave me years ago, I try to plant broccoli around labor day. But this year we have very high temps projected for the next week,. All days for the next ten days will be in the 90's or above. One day is projected to be 97*F. That is unusual for this time of year. Maybe the hurricane will help bring down the temps.

Zone 6A here and getting hotter every year. But I plant beets, carrots, kale and collards in mid July and all doing great. So are Asian radishes sown in early August, and I've just sown winter lettuces. I shade them and keep them watered until they germinate. Escaroles were sown in mid August also.

I’ve noticed that some crops planted in the spring, if planted late enough, will slow down during summer heat and come back with cooler summer weather. Being planted at a time that the weather is not quite brutal yet, they slowly get acclimated to the heat and do not fare as badly. I would like to experiment with this next year. I, too, struggle to start fall crops in the peak of summer. I’m in NW Arkansas, zone 6. The first frost is typically mid Oct. Our peak of summer temps typically refers to 90+ degree heat, rarely above 95 at our house. This, too, rarely lasts more than a week or two before a break into the 80’s intervenes. We average 33 days above 90 degrees.

This mid-Sept Heat is Stifling, our young fall crops are really taking it on the chin and all their other body parts. 97F as I type and the August drought lingers into Sept. If it weren't for our deep well and my shading contraptions all would be lost by now. Possible storms passing through later tonite, need the rain but not the stormy part. A possible tropical disturbance may come up the coast in a few days too but the jury is still out on that one.