A portable shelter may be provided with ground assembly, flex poles, and a cover assembly. The ground assembly may include a ground sheet or pad having rigid elements, such as metal ground poles along opposite sides. The ground poles may extend through sleeves on the ground sheet. The ends of the flex poles can be attached to fittings on the ends of the ground poles, with the flex poles flexed into an arc when the shelter is set up. The cover assembly includes a flexible cover made for example of fabric effective at blocking sunlight. Flex pole attachment devices, such as snap-on clamp fittings, may be spaced apart along opposite ends of the cover for attaching the cover onto the flex poles. Ground pole attachment devices may be spaced apart along opposite sides of the cover for attaching the cover to the ground poles.