Pediocactus simpsonii AKA Mountain Top Cactus is spread over hills and mountain areas of Central and Northern-Western US, growing in the places where winter snow is a norm. The plant on the picture was probably covered with snow not more than a month before. Couple miles from this spot snow was still laying solid on the ground.
The plants are frost tolerant, and the growth season is limited to spring only, when water supply from snow melt is guaranteed. In culture plants grow happily in humus-free substrate, and the requirement is to keep them wet for couple spring months. Watering in the summer makes no effect on plants, except may be late summer-early spring when plants may respond to it again. To see flowers in cultivation plants better be kept out of the heat of greenhouse. Too much daytime heat in the spring makes them abort flower development, but night frost is just fine.
Picture is taken in Grand Basin NP, NV