That's an excellent and very practical question for anyone living in a wet climate like the Pacific Northwest or similar rainy areas. I've wondered the same thing myself! From my experience and research, the effectiveness of drains on outdoor trash cans really depends on the specific design and quality of the bin.
Many mid-range to higher-end outdoor trash cans, especially those marketed as "weather-resistant" or "all-weather," do feature drainage holes at the bottom. These are small, often multiple, perforations designed to let rainwater escape so the bin doesn't turn into a stagnant, smelly pond. For light to moderate rain, these drains work reasonably well at preventing total waterlogging.
However, during the kind of heavy, persistent downpours we know too well, these small drains can struggle. They can easily become clogged with fine debris, sludge from garbage leaks, or even leaves. When that happens, water accumulates, making the trash incredibly heavy to move, promoting mold, and attracting more pests. The material matters too—plastic cans with thin walls might flex and crack, while thicker, rotational-molded polyethylene holds up better.
My advice? If you're buying new, actively look for cans that highlight "integrated drainage" or "bottom drain holes." Some even have a raised foot or a slight tilt to aid runoff. Regardless, placing the can under a slight eave or on a paved, slanted surface helps immensely. For existing cans without drains, you can carefully drill a few small holes in the lowest recess, but avoid weakening the structure. Ultimately, while drains help, they're not a perfect solution for monsoons—regularly emptying the bin and keeping it clean is still the best practice to manage the rain.