The invention provides a portable, free-standing shade structure that is resistant to wind. The inventive shade structure can comprise a frame and a sheet, or canopy, that is connected to the frame under tension at two or more different heights to create an uneven, hypar conformation in the sheet. The uneven, hypar conformation of the sheet transfers wind force to the frame so as to press the frame against the surface upon which the shade structure rests, thereby making the inventive shade structure resistant to the movement, tipping, lift, and vibration that typically results when a portable shade structure is exposed to wind.