Honestly, the short answer is that most urban trash cans are not dealing with anything close to their melting point during ordinary extreme heat. They are designed for it. The common plastic bins are usually made from HDPE or similar tough thermoplastics with UV stabilizers and heat-resistant pigments. HDPE does not start to soften until roughly 120°C, while even a dark bin in full sun on a very hot day might reach around 70–80°C at the surface. That is hot enough to make people uncomfortable, but it is still a long way from melting. What can happen without proper additives is UV damage, fading, and embrittlement over time, which is why stabilizers and durable coatings matter.
Warping is more about thermal expansion than melting. Designers use ribs, double walls, rounded corners, and thicker sections to add stiffness. They also avoid locking the bin down rigidly at every point; slotted holes, flexible mounts, and small expansion gaps let the material move as it heats and cools. Ventilation and feet that keep the base off hot pavement reduce heat buildup. Light colors or reflective finishes cut solar gain, while metal bins—usually powder-coated steel or aluminum—will not melt in summer heat, though thin panels can buckle if they are not braced properly.
Concrete and fiberglass bins are chosen where stiffness, weight, or fire resistance matters more. The real exception is fire. If someone drops a lit charcoal briquette or an aerosol can into a bin, no ordinary plastic container is happy about it. Cities handle that with metal liners, fire-resistant additives, smaller openings, and sometimes suppression systems. So for normal heatwaves, the challenge is mostly UV exposure and thermal expansion, not melting; the solution is smart material choice, UV stabilization, stiff-but-tolerant geometry, ventilation, and reflective finishes.