Dust, wind and the Santa Ana River channel
The river bottom and open land funnel wind through the area, and dry fall gusts can be strong. Dust is another companion. Fine grit settles on roofs, clogs drains and gutters and wears surfaces. On flat industrial roofs, dust and debris block scuppers and let water pond, which stresses the membrane.
Summer heat bakes every kind of roof, but dark membranes and metal panels warm especially fast. Seams open and close with the daily temperature swing. Ranchettes with older metal roofs may show rust at fasteners, and the screws themselves can back out as the metal flexes. Small gaps become leak paths during the first heavy storm of the winter.

