We AI in late April in years when we AI. #1 big item is feed and feed quality. If feed is great (especially adequate energy) it will have better success any time of year. Judge that on good: cows gaining weight and bad: cows holding own or losing weight. To make sure be supplementing 2 weeks prior and some beyond. Is a bigger concern to me if semen is rare or expensive. Energy is a concern in summer grazing unless you do more than basic perennials.
Shade access and low stress would be critical both getting ready, doing AI work and for multiple weeks after to minimize stress and get embryos attached.
Decent and correct minerals are key. Nothing to do with this so a drift: changed source of "high quality" minerals this year. Have a cow sired by an odd outside AI bull that breeds like a clock, raises a nice calf and has fuzzy hair like no other one here. I tolerate her because of her fertility and calf quality. This year, she is slick as a peeled onion. Hot summer, drought, armyworms, all - difference is minerals.
Other #1 issue :D would be if cattle are environmentally adapted. Hair, BSC, and such will tell the tale. Here we fight the double battle of climate and fescue base so that is just what I experience. Read up on Bonsma traits really helps. But like it has been said, expect lower % merely due to temperatures. Sorry to be no help.
