Great question—nothing ruins a good sit faster than a seat that feels like a frying pan. For a street bench that stays reasonable in summer, I’d focus on material first.
Wood is my top recommendation. Solid hardwood slat benches made from teak, ipe, white oak, or thermally modified ash absorb and release heat much more gently than metal. Even after hours of direct sun, a light-to-medium stained wood seat is usually fine to touch and comfortable to sit on. If you want less upkeep, thermally modified wood or a quality oil finish will hold up outdoors without getting hot like black steel.
Recycled plastic and composite lumber, often called HDPE, are also excellent. Parks use them because they resist weather, need no painting, and don’t conduct heat like metal. Stick with lighter colors such as sand, gray, or cedar. Dark brown and black plastic can still warm up on a 95°F day, but they’re generally far more forgiving than solid metal.
If you prefer the look of metal, go with powder-coated aluminum with wood or plastic slats. Aluminum itself conducts heat, but a light matte finish reflects more sun and cools down quickly in shade. The slatted seat is what saves your legs, so avoid solid metal panels.
What I’d avoid: solid dark steel, dark painted metal, black solid plastic in full sun, and dark concrete or stone. If metal is your only option, choose perforated or slatted seating in a light color, and place it under a tree, umbrella, or shade structure.
A few search terms worth using: “thermally modified wood bench,” “HDPE park bench,” “recycled plastic bench,” or “FSC teak bench.” Brands like Polywood, Loll Designs, and commercial lines from Maglin or Victor Stanley make good options, but many local park suppliers carry similar heat-safe benches. If you can, test the bench at the hottest part of the day with the back of your hand—if you can hold it there for five seconds, it passes the summer test.
One last tip: finish matters as much as material. A matte, light-colored surface can run noticeably cooler than the same material in gloss black, and slatted designs help airflow carry heat away instead of baking the seat.