https://isre2005.net/cleaning-grill-cover/
Q: Can I wash my grill cover in the washing machine? A: Washing your grill cover in the washing machine isn't recommended. While it doesn't automatically mean the cover will be damaged as some users claim they do so without any harm, but there are others who also reported damage as a result of agitation or harsh chemicals used in the washing. Source: https://bbqbarbecuegrill.com/other/how-to-clean-weber-grill-cover/ Q: How do you get mildew off a grill cover? A: Mix a bucket of hot water and bleach, using 1/4 cup of bleach to 1 gallon of water. Using a scrubber-type sponge, wipe the grill cover with the bleach solution to remove the mold. Allow the bleach solution to work for five minutes.