That's an excellent question, as extreme heat is a real concern in many urban environments. The performance of a plastic trash bin in high temperatures largely depends on the type of plastic used. Most modern municipal bins are made from high-density polyethylene (HDPE) or polypropylene, which are engineered for durability.
In general, these materials can handle temperatures up to about 120-140°F (49-60°C) before they begin to soften. You might notice some slight warping or flexing on the hottest days, especially if the bin is a dark color that absorbs more solar radiation. However, they are designed not to melt or become unusable under normal conditions. Prolonged exposure to direct, intense sunlight can lead to brittleness over time, making the plastic more susceptible to cracking.
For urban use, it's wise to place bins in slightly shaded areas if possible and avoid pouring extremely hot liquids directly into them. Overall, while no plastic is entirely immune to heat effects, quality bins are surprisingly resilient and specifically formulated to withstand the challenges of city life.