May is a great month if you're looking for a good deal. The best sales—when discounts are often as much as 50 percent—come around Memorial Day.

This is also a good time to buy paint and wood stain as well as decking, siding, and roofing if you want to take advantage of the weather to spruce up your home.

May is probably not the time to buy jewelry because prices typically rise around Mother’s Day (Sunday, May 14, this year), according to Maria Lalonde, a shopping expert with Offers.com. Send mom some flowers instead.

Consumer Reports tracks the prices of the products we test so we can tell you, month by month, what to buy on deep discount.

Products covered this month: mattresses; gas grills; air conditioners; vacuums; roofing, siding, decking; pressure washers; paints/stains; and strollers.

Mattresses

If you're shopping for a new mattress, you could be overwhelmed by the variety of choices and the prices, ranging from too-low-to-believe to astronomical. But there's good news: Our years of testing have shown that whatever type you choose, you don't have to spend over $1,000 for a comfortable, supportive mattress. Keep an eye out for sales this month and you could score an even better deal.

Shopping Tips: 

  • Test-drive several models. Buy at a store, not online or over the phone, unless you've already tried the identical mattress in a store. A product manager for Tempur-Pedic told us that more online customers return their mattresses than shoppers who buy in a store.
  • Shop back to front. Start out with the least expensive bed from a few top brands, and work your way up in cost. Stores keep the priciest models up front, so head to the back of the store first. Our mattress buying guide has lots of additional shopping tips. We put mattresses through tough tests; see which ones came out on top in our ratings

Gas Grills

The days of backyard barbecues are quickly approaching, and the quality of your gas grill plays a role in the success of the hot dogs and hamburgers you'll be cooking. If you're planning to buy a gas grill this month, hold out for Memorial Day sales, when you will likely find the best deals.

Whether you're a first-time buyer or a seasoned grill master, there’s a gas grill to fit every cooking style and budget. Check our gas grill brand reliability information in our ratings to find the lowdown on high heat.

Shopping Tips:

  • Check the cart, wheels, lid, and firebox. Look at—even jostle—the assembled grill from several points to test sturdiness; the more stable, the better. Stainless-steel carts with seamless construction and welded joints are usually sturdier than painted-steel carts assembled with nuts and bolts. While you’re at it, make sure to avoid grills with sharp metal corners and edges.
  • Know your menu. A basic grill is fine for cooking burgers and hot dogs, but if you also enjoy delicate fish and sizzling steaks with sear marks, look at the temperature-range scores in our ratings. They indicate just how versatile the grill is. The higher the score, the better the grill is at cooking a variety of foods. 

Room Air Conditioners

Air conditioners go on sale before the hot weather sets in and again when it starts to get cooler. There may be fewer models available at the end of the season, however, so it's smart to look for sales now.

Our air conditioner buying guide and ratings will help you spot the right model. (Need a whole-house system? Check our central air conditioning buying guide.)

Shopping Tips

  • Size it correctly. This will ensure that the unit will work properly and save you money on energy costs. An air conditioner that's too small won't do a good job cooling a room and will also use up more energy than necessary. One that's too big will also waste energy and cool the area so quickly that the moisture level could remain high, leaving you with a cold, clammy space. Check our buying guide to help you find the right size. 
  • Note the noise. Models that scored Excellent or Very Good in our noise tests (we measure how loud they are on both low and high settings) are so quiet that the only sound you might hear is the fan running. But air conditioners that scored Fair for noise could disturb light sleepers even when set on low and are far too loud when set to high.

Vacuums

Spring-cleaning season is officially here, and if your vacuum is due for an upgrade, you’re in luck. April and May are great times to find discounts on all types. You’ll find a range of designs, sleek shapes, and cool colors, but what matters most is how well they clean. Look for one that has features that appeal to you, but make sure it fits your cleaning needs as well.

Shopping Tips: 

  • Try it out. Even if you order online, go to a store first. Push, pull, turn, and lift the vacuum cleaners you're considering. If an online price is low, see whether the store will match it.
  • Consider the features. Pet owners, take note: Upright and  canister vacuum cleaners that excel at regular jobs tested best in show for picking up pet hair. Canister vacuums tend to be quieter as well. Protect bare floors by selecting a vacuum with a switch that can deactivate the brush. For more features, check out our ratings.

Roof, Siding, and Decking Materials

If you need another reason to get started on your home improvement projects, great deals on materials this month may be just the motivation. 

New siding can give your home an immediate makeover and help make it easier to sell later. Replacing or adding a deck can provide a relaxing getaway in your own backyard. And although you can put off some home repairs indefinitely, a leaky roof isn't one of them. These projects are big undertakings and often require hiring labor, but saving money on the materials can help stretch your budget. 

Shopping Tips:

  • Roofing: Suppliers sell roofing by the square, or 100-square-foot area. To estimate how much you'll need, multiply the overall length and width of each roof section in feet to determine its area and add 10 percent to allow for waste. Keep an extra bundle of shingles for minor repairs, like after a heavy storm. Check out our roofing buying guide for more tips. 
  • Siding: We recommend having a professional install siding. An installer will calculate how much your home needs, but you can make a rough estimate without climbing a ladder—and avoid overpaying someone you hire. Use our ratings to help you determine which material—vinyl, plastic, fiber cement, or wood—best suits your taste and budget.
  • Decking: When pricing the materials, be sure to figure in the cost of railings, stairs, and structure support as well as the planks underfoot. If you're hiring a pro, note that the cost of labor—either to build a new deck or to replace worn planking on an existing structure—can easily exceed the cost of the materials. Our decking buying guide can help you make the best choices for your budget.

Pressure Washers

If you want to invest in a pressure washer, you’ll find good deals in May. Whether it's motor-oil stains or mildew on a deck, pressure washers can do the job in a fraction of the time it takes using a brush and bucket of water. But keep in mind that because pressure washers deliver a concentrated and powerful stream, they can cause serious injury and damage property if not used properly.

Use Consumer Reports’ safe operating techniques to stay out of harm’s way, and our ratings will help you make sure you get the right model.

Shopping Tips:

  • Cover your bases. If you need to use soaps, solvents, or other additives, consider one that has a built-in soap tank. Tool and cord storage is a plus, as are wheels for heavier models.
  • Rent one instead. Buying a unit will pay for itself in a few years as long as you take care of it. But if you want to skip the hassle of upkeep and storage, you can always rent a power washer instead. 

Exterior Paint and Wood Stains

Sprucing up your home is more affordable this month if you take advantage of deep discounts on external paints and wood stains. Buying a can of paint should be easy, but walk into any home center or paint store and you’ll see just how confusing it can be to make a choice, especially if you're looking for a good deal. We test dozens of interior and exterior paints in a variety of finishes to help you find the best one for the job and your budget. For more painting tips, see our interior and exterior paint buying guide and ratings.

Wood stains provide a layer of protection that can keep your deck looking great for years. Many will also protect fences and siding. The most durable options in our ratings are often the most expensive, but their longer life should save you money over the long haul.

Shopping Tips:

  • Exterior Paint: When selecting a color, it's smart to take a cue from other houses in the neighborhood as well as from nature. For example, ochre and forest green play well in wooded regions; earth tones are more suited to desert landscapes. Once you’ve narrowed your choices, buy small cans for testing. Observe how different levels of light affect the color throughout the day.
  • Wood Stains: The best opaque treatments tend to last the longest, but you may prefer a semitransparent or clear finish for aesthetic reasons. Today's wood stains have to meet environmental standards for lower volatile organic compounds, which are linked to pollution, smog, and respiratory problems and can cause headaches and dizziness. Some may even be carcinogenic. Top stains from our tests meet these standards.

Strollers

You'll find great prices on certain baby products this month, especially if you need a new stroller. When considering your options, you obviously want your baby to be safe and comfortable. But think about yourself, too, because you're the one who'll be pushing it.

There's a wide price range among types and brands in our stroller ratings. What makes one stroller cost $100 and another $1,000 or more? Several features drive up the price, such as accessories, but we've found good models in a wide range of prices.

Shopping Tips:

  • Consider your environment. If you're a city dweller who relies on subways, buses, and cabs, you'll need a lightweight but sturdy stroller that folds quickly and is compact. If you'll be pushing it through snow or on unpaved roads or grass, a model with large wheels is a great option.
  • Check certification. Look for a sticker on the stroller or on the packaging showing that the manufacturer takes part in the certification program administered by the Juvenile Products Manufacturers Association (JPMA), which tests the brakes, stability, and other important safety features.