The wettest spring in thirty years brings wildflowers and a carpet of green to the dunes of the Sierra El Rosario of the Pinacate volcanic area. Purple flowers are sand verbena (abronia villosa), and white flowers are dune evening primrose (oneothera deltoides). This peak bloom lasts only a few days and occurs this strongly in only the wettest of years. This is one of the driest areas in North America and receives on average less than 10 cm of rain per year. Years with no rain at all are not uncommon.