SavingAdvice.com Blog Unfortunately, Costco is closed on Memorial Day. So if you need to pick up some burgers for your backyard barbecue on the 31st, you won’t be able to head to your favorite warehouse store. But luckily Costco is still having a big Memorial Day sale to celebrate the holiday. Members can save on everything from apparel to mattresses to appliances. To help you put together your shopping list, we’ve rounded up some of the best deals below. Mattresses If your mattress is feeling old and lumpy, now is a great time to replace it thanks to Costco’s great Memorial Day deals. A bunch of mattresses are on sale including the Thomasville Gel Rest Split King Mattress. Currently you can save a whopping $1,200 on it.