That's a great question! Keeping rain out of your outdoor trash bin is crucial to prevent a soggy, smelly mess and to stop the bin from becoming overly heavy. From my experience, not all lids are created equal when it comes to weather protection.
The absolute best type of lid for keeping rain out is a domed or convex lid. Its rounded shape doesn't allow water to pool on top; instead, rain simply slides right off the sides. This design is far superior to a flat lid, where water can collect and eventually seep in through the seams.
Other excellent options include secure hinged lids that are attached to the bin. These stay in place during wind and storms, ensuring the opening is consistently covered. For maximum protection, look for lids with a tight seal or gasket around the rim and locking or latching mechanisms. These features not only keep rain out but also deter pests like raccoons and stray animals from getting in.
In summary, prioritize a domed shape for the best water runoff, and pair it with secure hinges and a good seal for a truly weatherproof setup. A simple, loose-fitting flat lid is often the least effective against persistent rain. Investing in a bin with a well-designed lid saves you from dealing with messy, overflowing wastewater later.