The short answer is to keep the wood dry, use rot-resistant or treated timber, and make the bench hard for termites to reach. In a humid climate, moisture and hidden soil contact are your biggest enemies, so focus on wood choice, sealing, placement, airflow, and regular inspection.
Start with the wood itself. If you are buying a bench, choose naturally dense woods such as teak, ipe, cedar, white oak, or cypress. These contain oils and tannins that resist both decay fungi and termite damage far better than pine, fir, or soft maple. If you already own a bench made from untreated softwood, apply a borate wood treatment on bare wood before any stain, paint, or sealer. Borates penetrate the grain and kill termites and wood-boring insects while also slowing rot.
Next, manage moisture. Apply a high-quality exterior wood sealer, marine varnish, or exterior-grade paint every year, or every six months if the bench sits in full rain. Coat the end grain and joints heavily because those areas soak up water fastest. Clean off dirt, mildew, and any soft wood first, and let the bench dry before sealing. Never seal over existing rot; remove or repair the damaged section instead.
Keep the legs off wet ground. Set the bench on stone, concrete, brick, or rot-resistant blocks rather than directly on soil or grass. If you must place it on a wooden deck, use plastic or metal feet to break the moisture path. Trim back plants, mulch, and leaf litter so they do not pile against the legs or underside. Termites often enter through damp hidden contact points, so this step alone prevents a lot of problems.
Improve airflow. Place the bench where air can move around it after rain, and avoid pushing it against walls, fences, or dense shrubs. Remove wet cushions or fabric covers promptly so they do not hold moisture against the wood. If you store items under the bench, keep them clear of the seat slats.
Inspect every few months. Look for mud tubes, tiny holes, sawdust-like frass, soft or dark patches, and cracked finish. Solid wood sounds firm when tapped; rotted wood sounds dull or feels spongy. If you catch soft spots early, scrape them out and repair them with wood hardener or epoxy filler. For active termites, do not rely only on surface sprays. Use termite bait stations nearby or call a professional, especially if you see mud tubes on the legs or ground.
During the wettest season, a breathable cover can help, but make sure it does not trap condensation. A vented outdoor furniture cover is best. If possible, move the bench under a covered porch or add a small roof or pergola. Even reducing direct rain exposure by a few hours after each storm makes a huge difference.
Protecting a wooden outdoor bench in a humid climate is not a one-time job. Choose rot-resistant wood, treat it, seal it, keep it off the ground, let it breathe, and check it regularly. That combination will keep termites and rot away far longer than any single product alone.