How can I cover patio pillows?

Sure, you can purchase new covers or sew them. here are my tutorials for how to make a pillow.

I had faded and very fitted covers on my rattan porch chairs. These are very comfortable chairs with springs and nice fat cushions, back and seat. I know how to sew but did not want the work of making the fitted covers that would be necessary. I bought four very inexpensive fleece blankets. and just sort of roughly basted them onto the cushions. These have lasted 3 years so far. But Maine summers are short! (covers are because of rain)

If I were doing that, I'd remove the old covers and just use the insides if they're ok.

Years ago I Purchased some stretch terrycloth cushion covers, they’re sort of like a fitted sheet with a tie on the bottom are easy to remove and washable in the perfect solution for my need.

I’m not sure if you can still purchase this type of cushion cover or construct them on your own if you have sewing abilities.

When you buy the new material, be sure it is outdoor material. Regular material will sunfade.