I’d skip anything that drinks water or has places for water to hide. For urban outdoor furniture that you want to wipe down after a rainstorm, avoid unsealed wood, reclaimed wood, and rough-sawn timber; once water soaks in, you get swelling, stains, mold, and you’ll be re-oiling or sanding instead of just wiping. Also avoid natural wicker, rattan, and woven seagrass—they look great, but rain gets into the weave and dries slowly. Fabric cushions and sling seats are another no if quick wiping is the goal; open-cell foam and seams hold water. Porous stone, unglazed concrete, and rough terracotta are hard to dry and can grow mildew. For metal, skip untreated steel, mild steel, and cast iron unless the coating is perfect—chips lead to rust stains on paving. Also be wary of chipped powder coating and tight crevices where water sits.
What I’d choose instead: powder-coated aluminum, stainless steel (316 if you’re near the coast or salted roads), sealed HPL compact laminate, glazed ceramic, glass, and sealed teak or acacia with a smooth finish. HDPE is also practical if you like the look. Look for simple shapes, sloped or open seats, drainage gaps, and removable cushions you can bring inside. A quick wipe with a microfiber cloth should be enough. Avoid high-maintenance materials and fussy joins; in a city, easy rain cleanup is mostly about non-porous surfaces and no water traps.