Also depends on what they are grazing. Mine are on annuals right now. Temps in the upper 80's, and the white, cream, and red cows are out eating. The black cows with a little ear are out there too. The others are laying by the water wishing they had shade. 2-3 more days and it will cool down a bit. 7-10 and They'll have shade until september, but they will be on fescue. I haven't had my cows long enough to cull hard for cows adapted to my farm, so even with the shade if they are on fescue they will be panting and losing condition. My cows look worse in August than January as a general rule. So yes, they will probably need shade, but you can manage around it. Now is the time, before the fences go up... Square fields may be more efficient, but how efficient is a field you can't graze. Might have to get creative. Good luck.