Honestly, the first thing I’d do is stop trusting the furniture’s own weight. On a high balcony, wind gets funneled and even a reasonably heavy chair can start sliding. So I’d make a simple system: anchor, weight, and store.
For chairs, tables, and benches, use nylon straps or bungee cords rated for outdoor use. Loop them through the frame and around the railing or a nearby anchor point. Don’t just tie the legs together; that won’t stop a gust from lifting the whole thing. If you can’t drill into the wall or railing, use railing clamps, heavy-duty zip ties, or a chain with a lock. Check your building rules first, because some balconies prohibit attaching anything to railings.
Weight is your friend. Fill planters with sand or gravel, or use water-filled weights and sandbags. Put them on the lower shelf of a side table or inside a storage bench if the furniture allows. For lightweight folding chairs, I’d replace them with heavier metal or wood furniture, or keep them folded and strapped to a wall rack when not in use.
Umbrellas are the biggest flight risk. Always close them when you’re done, and lay them flat or bring them inside before a storm. If you have a grill or small table, lock the wheels or use rubber feet to increase friction. Arrange furniture close to the wall and out of the wind tunnel between buildings, not right at the railing edge.
On windy days, do a quick sweep: stack what you can, bring cushions inside, and clip a strap over anything that could become a projectile. If you’re a renter, temporary solutions like weighted bases, tension rods, and adhesive-free railing hooks are your best bet. And if something does blow over, tell your neighbor and help retrieve it—it’s better than pretending it didn’t happen.