I have seen a lot of blogs where people put tons of cushions outside and I wondered that myself. My mother usually puts her chair cushions in the shed when not in use. But I have found that because my balcony is covered, the rain is not usually a huge issue. Here are a few tips for keeping cushions and furniture clean on a balcony.
1. Buy Outdoor Pillows
My red and white pillow is actually designed for being outdoors and the fabric is water resistant so a little bit of rain doesn't hurt it. I use a damp cloth to wipe it down when it gets dirty, but I will be honest and say that it has faded a lot in the last few years and definitely seems a lot dingier. This particular pillow is from West Elm and besides those issues I have had no issues with the quality of the pillow! It is still big and comfy.
2. Make Your Own Pillows Using Water Resistant Fabric
The green and blue pillow is actually covered in a fabric napkin, which is designed to clean up easily! You can also buy fabrics designed for the outdoors, like my West Elm pillow (I always found Fabricland actually had cuter outdoor fabrics than indoor! My ottoman is covered in outdoor fabric and it is great for repelling spilled water!)
3. Make or Buy Pillows with Removable Covers
My flamingo pillow is just a cover I quickly sewed up from a couple tea towels last summer. This pillow doesn't usually get wet, being on the inside of the balcony, but it does get dirty. Mostly because it randomly falls on the ground a lot. But the cover is removable so I just pop it in the wash and it is good as new again! The blue/green pillow also has a removable cover. I don't worry too much about the pillow inside, but they are actually washable and if I really thought it was funky, they are also very inexpensive to replace.
As for the dirt and grim that comes with a balcony, there is no cure for preventing that (if you have one, please let me know!). I have to go out there before guests come over and wipe everything down with warm soapy water and flip the striped chair cushions over. The chair cushions actually don't get that wet either and flipping them over tends to take care of any dirt.
Sometimes I use a scrub brush to really clean the furniture. It was inexpensive and does a quick job of it. I also keep a mat by the back door for people to wipe their feet off on when coming back in from the balcony, though I am not a stickler for keeping shoes off my floors or anything like that.