Honestly, the best way to winterize urban outdoor furniture in a cold climate is to treat it like you're putting it into hibernation, not just tossing a tarp over it. The real enemies are moisture, freeze-thaw cycles, road salt, and wind. In a city, you also have limited storage, pollution, and sometimes shared spaces, so a little planning matters more than expensive gear.
The short answer: store anything fabric indoors, treat the frames based on material, elevate what stays outside, and cover it with a breathable, secured cover. If you do only one thing, get cushions and textiles out of the weather. Damp cushions left under a cover are a mold factory, and freeze-thaw can ruin foam.
Start with a dry, mild day before the first hard freeze. Clean everything with mild soap and water, then let it dry completely. Dirt and grime hold moisture, which leads to rust, mold, and cracked finishes. Pay extra attention to joints, screw holes, and crevices where water hides. For metal furniture, touch up any scratches with matching paint and apply a thin coat of wax or rust inhibitor. For wood, clean it, let it dry, and apply a quality oil or sealer. Teak can weather gracefully, but a little oil helps it survive winter. Wrought iron may need sanding and repainting where rust appears. Aluminum benefits from a coat of automotive wax. Resin and plastic should be washed and dried; avoid harsh solvents.
Then move what you can. Cushions, pillows, umbrellas, small side tables, and removable glass tabletops should go indoors. A closet, basement, garage, or even a dry storage bench works. Use breathable storage bags or cotton sheets, not sealed plastic, because trapped moisture causes mildew. If you have no indoor space, at least bring cushions inside during storms and keep them elevated in a dry spot.
For furniture that must stay outside, elevation is key. Put legs on pot feet, bricks, or plastic risers so they aren't sitting in snow, ice, or puddles. Group pieces together in a sheltered corner, but leave space for air to move. Use a breathable, waterproof cover sized to the furniture. A loose tarp that flaps in the wind can scratch finishes and trap condensation. Secure covers with bungee cords or straps, especially on balconies and rooftops where wind is stronger. If you have a glass table, remove the glass if possible; snow load and ice can crack it. If it can't be removed, cover it with a rigid board and then a cover.
Umbrellas should be closed, cleaned, and stored indoors. If that's not possible, secure them tightly so they don't open in a gust. Fold chairs if you can, and stack them only if the finish won't rub. For wicker and rattan, make sure it's completely dry before covering, since trapped moisture makes it brittle and moldy.
In urban settings, road salt is a big issue. It can corrode metal legs and stain wood. On a mild day above freezing, wipe down or rinse salt spray from metal and sealed wood, then dry thoroughly. Don't use water in freezing temperatures, because it can freeze in joints and cause cracks. A damp cloth followed by a dry towel is safer.
Finally, check your setup monthly. After a snowstorm, brush snow off with a soft broom instead of chipping ice with a shovel. Make sure covers aren't sagging and holding water. Re-tighten straps after windy days. If you see rust or mold, deal with it right away.
The best winterizing plan isn't complicated: dry everything, store fabrics, protect materials, elevate, cover with breathable fabric, and secure against wind. That routine will get most urban outdoor furniture through a cold climate without turning spring into a repair project.