My broodies usually hatch in that time period, June through August. As far as health and survival of the chicks with a broody, that’s a good time of year. I just wish my hens went broody earlier in the year so I wouldn’t have to hatch some in an incubator and brood them myself.
As OGM said, as long as you can brood them you can hatch at any time of the year. My brooder is in the coop. I’ve put chicks in it straight from the incubator in February when the outside temperatures were below freezing and in August when we were having a ridiculous heat wave. They all did well.
With my broody hens hatching as late as they do it’s pretty normal for me to have some pullets start laying in December, and I do not provide supplemental light. They tend to wait a little longer to start laying when they hatch late because of the length of the days, but they do lay and lay well once they start. If you are hatching them for meat you may have trouble finding a good day to butcher late in the season once the weather goes bad but I always manage. If you are hatching them to sell, you may have a problem finding a buyer for young chicks, but you may have a good market in the spring for pullets that have just started to lay, though you will have to feed them through the winter so your costs will be higher if you depend on them foraging for part of their feed.
There is no real problem hatching later in the season but they will mature late in the season. It just depends on why you want to hatch and how you are set up. Good luck!
