This polypore always seems to grow alongside Stereum ostreatus (False Turkey Tails). It has a suede-like, pretty pink cap with a creamy undersurface that looks like squiggly ridges all squashed together. The pink color is more pronounced in damp weather.
Summer Oyster mushrooms look very much like those that grow in cooler weather, but have different spores, and will grow in the hotter, dryer weather.
There's a good explanation here: http://www.mushroomexpert.com/pleurotus_pulmonarius.html