If I had to pick one material combination for most rainy cities, I’d choose a powder-coated aluminum frame with recycled HDPE slats. It offers the best balance of weather resistance, low maintenance, and upfront cost. Aluminum won’t rust like mild steel, and a good powder coating protects it from scratches, moisture, and road salt. HDPE does not absorb water, rot, splinter, or crack, and it handles constant damp and UV exposure well. It is also easy to clean with soap and water and does not need annual oiling.
For a premium, long-life option, marine-grade 316 stainless steel is excellent, especially near the coast or where de-icing salt is used. It is strong and highly corrosion-resistant, but it costs more and can feel hot or cold in extreme weather. Use a brushed or powder-coated finish, stainless fasteners, and avoid lower-grade 304 steel in harsh conditions.
Teak is still a great choice if you want natural warmth. Its natural oils help it resist rot, and it can be left to weather to a silver-gray finish. However, teak needs more maintenance if you want to keep a honey tone, and in very wet, shaded urban spots it can become slippery. Use plantation teak and raise the feet so water can drain.
Cast concrete or granite can work for permanent seating, but these materials are heavy and may stain unless properly sealed. For low-maintenance public furniture, recycled HDPE is usually the most practical choice. Avoid untreated softwood, mild steel, wicker that traps water, and furniture with poor drainage. In a rainy climate, design details matter as much as the material: drainage gaps, sloped seats, stainless fasteners, breathable covers, and raised feet will make any outdoor furniture last longer.