IME, you will get much more shooting done in the first 2 weeks of June: young pups have not associated gunfire with danger yet ......
Later in the summer, after they have been shot at a few times, prairie dogs will hole up after the first couple of shots..... at some of the more accessible towns I shoot at, they run for their holes if a vehichle slows down when passing by on the road.
It is also cooler in June than later in the summer.