That's an excellent and very practical question for anyone living in a rainy area like the Pacific Northwest, parts of the UK, or tropical regions. The short answer is: it completely depends on the design and quality of the lid. Not all trash can lids are created equal when it comes to keeping water out.
Standard, basic lids often have gaps or simply sit on top, allowing wind-driven rain to seep in. This can lead to a soggy, heavy mess, attract pests, and cause unpleasant odors. However, many modern outdoor trash cans are specifically designed for weather resistance.
Look for features like a true tight-sealing gasket or rubber seal around the rim, similar to those on high-quality coolers. Snap-down or lockable lids that create a positive seal are far superior to loose-fitting ones. Dome-shaped or tapered lids are also beneficial as they shed water away from the seams instead of letting it pool on top.
For extreme climates, consider garbage cans marketed as "animal-proof" or "weather-tight," as they typically have the most robust sealing mechanisms. Even with a great lid, proper placement matters—avoid putting your can under downspouts or in natural drainage paths.
So, while a flimsy lid will likely let water in, investing in a can with a purpose-built, sealed lid can absolutely keep your trash dry. It's all about choosing the right tool for your environment.