Short answer: mostly yes for direct rain, but not completely. A domed top does what a roof does—it sheds water sideways instead of letting it pool on a flat lid. On a typical city bin, the dome also overhangs the opening, so ordinary vertical rain tends to run off the curved surface and drip past the rim rather than fall straight into the bin. That is why domed designs are common on sidewalks, in parks, and at bus stops.
But “keep rain out” depends on the details. A recessed side opening helps a lot, especially if it faces away from prevailing wind. A wide, open mouth under a shallow dome is much less protective. Wind-driven rain can travel almost horizontally and slip through gaps around a flap, a push door, or the rim. Water can also run down the pole or mounting bracket and find its way inside. In heavy storms, even a good dome is more of a rain shield than a waterproof seal.
Maintenance matters just as much. If the internal liner is torn or the drainage channel is blocked, water can collect at the bottom and soak the contents. Some bins are deliberately not drilled at the base, because holes can leak litter juice onto the street; that trade-off can leave rainwater trapped inside. Wet waste and condensation also make the bin feel damp even when rain hasn’t gone straight in.
So, do domed urban trash bins really keep rain out? They reliably block most direct rainfall and keep the top from becoming a puddle, but they are not fully rainproof. The best designs combine a deep overhang, a sheltered opening, a drainable or sealed liner, and regular emptying. A dome helps—but the opening, drainage, and upkeep are what decide whether the rubbish inside actually stays dry.