That's an excellent question, and one that city planners and manufacturers take very seriously. From my experience living in a rainy coastal city, I can tell you that modern urban trash cans are generally designed to handle heavy rain quite well, though with some important caveats.
Most public bins you see today, especially the newer models, are engineered with weather resistance in mind. They typically feature integrated drainage holes at the bottom. This is the key feature. When rainwater gets into the bin—either directly or from discarded liquid items—these holes allow it to drain out slowly, preventing the bin from becoming a stagnant, waterlogged mess. This helps control weight, odor, and mosquito breeding.
The materials also play a huge role. High-density polyethylene (HDPE) or powder-coated steel are common. These materials don't rust or corrode easily and can withstand constant exposure to moisture. The lids are crucial too; a well-fitted, sloped lid sheds water away from the opening, minimizing how much rain gets inside in the first place.
However, their performance has limits. In a true torrential downpour or hurricane, any bin can be overwhelmed. If the drainage holes become clogged with sludge or debris, water will pool. Wind can blow lids open or drive rain sideways into the bin. The real issue often isn't the bin itself failing, but the contents becoming a sodden, heavy mass that's difficult for collection crews to handle.
So, while they're not submarine-grade, standard urban trash cans are surprisingly resilient. Their design focuses on managing, not completely preventing, water ingress. For areas with frequent extreme weather, you might see specialized bins with sealed compartments for waste vs. recycling, or even elevated designs. The next time you pass one in the rain, you can be fairly confident it's holding up as designed.