That's a common and frustrating problem! The sun's intense heat can definitely warp plastic lids over time, making them difficult to close properly. Here are some natural, practical solutions I've found work well.
First, consider relocation. If possible, move your bin to a shaded area, like under a tree, beside a fence, or under the eaves of your house. Even partial shade during the hottest part of the day makes a huge difference. If shade isn't available, create your own. A simple outdoor umbrella or a DIY shade screen mounted on a post nearby can shield the bin.
A reflective cover is a great defense. You can purchase a fitted, reflective trash can cover or get creative. Wrapping the lid (or the entire bin) with a reflective car sun shade or aluminum foil-backed insulation tape helps bounce the sun's rays away. Just ensure any adhesive is suitable for outdoor plastic.
Regular maintenance goes a long way. Clean the lid and bin regularly to remove grime that can attract more heat. Applying a UV-protectant spray or a coat of automotive vinyl protectant a few times a year can help shield the plastic from ultraviolet degradation, which weakens it and makes it prone to warping.
For a more permanent fix, consider upgrading. When it's time to replace the bin, look for models made with thicker, commercial-grade plastic or those specifically labeled as UV-resistant. Some are even made with materials less prone to heat distortion.
Finally, a simple habit change: try to empty your bin in the morning. Leaving it in the sun all day while full traps heat inside, accelerating warping. An empty bin heats up less. With a combination of shade, protection, and care, you can keep that lid fitting snugly for seasons to come.