I thought spring was the only time we would have wild flowers in the field. But I found these the other morning while I was out walking. I consulted my handy Wild Flowers of Texas leaflet and I think they are called Rain Lily.
Rain Lily (Cooperia pedunculata) appears like magic a few days after heavy rains, from spring to fall. The blossom opens slowly at dusk, gradually expands during the night and appears in full flower the next morning.