That's an excellent and very practical question for anyone dealing with frequent rain. As someone who has battled soggy trash bins myself, I can tell you that while drainage holes are a crucial first line of defense, they are often not *enough* on their own to fully prevent waterlogging in a very rainy area.
Think of those small holes as a relief valve, not a complete solution. They're designed to let out incidental rainwater that splashes in or a small amount of condensation. During a persistent downpour, however, they can easily become overwhelmed. Debris like leaves, sludge, or fine garbage can clog them. More importantly, if the bin sits flat on the ground, water can pool around the bottom, creating a seal and preventing proper drainage, leading to a smelly, stagnant soup at the bottom of your bin.
So, what can you do to help your bin? First, elevate it slightly. Placing it on a couple of bricks or a small platform allows air to circulate underneath and helps water drain more freely from the holes. Second, make regular cleaning part of your routine. Hose out the bin and check that the holes are clear of blockages. Finally, consider a bin with a tight-fitting, waterproof lid or using a simple waterproof cover to minimize the amount of rain getting in the first place.
In short, the drainage holes are essential, but in a truly rainy climate, they work best as part of a strategy. Combining them with elevation, maintenance, and a good lid is your best bet for a drier, cleaner, and less odorous outdoor trash bin.