That's a very common and practical concern for anyone living in a rainy area! The short answer is: while water can get inside, it typically shouldn't "fill up" a properly designed outdoor bin. Here’s a more detailed look.
Most quality outdoor trash bins are built with this in mind. You'll often find small drainage holes at the very bottom of the bin or its inner bucket. These allow any rainwater that seeps in—from lid gaps or when you open it—to slowly drain out, preventing it from becoming a mini swimming pool for your garbage.
However, several factors can lead to a soggy mess. If the drainage holes become clogged with debris, leaves, or sludge, water will accumulate. A cracked or damaged bin, or a lid that doesn't seal well, will obviously let in more water. During extremely heavy, prolonged downpours, even good drainage can be overwhelmed.
To keep your bin from holding water, make a habit of checking and clearing those drainage holes every few months. Position the bin on a level, slightly elevated surface if possible, not in a natural dip where water collects. Using sturdy, sealed garbage bags and tying them tightly is your first line of defense for the trash itself. For very wet regions, consider investing in a bin specifically advertised as "weatherproof" or "heavy-duty" with a tight-sealing, gasketed lid.
So, while you might find some water at the bottom after a big storm, a well-maintained bin should drain and not fill to the brim. A little proactive care goes a long way in keeping your outdoor waste dry and manageable, even in the rainiest climates.