As warm weather thaws in the Northern states, something inside investors' minds snaps. Perhaps with more barbecues going on, investors don't want to spend time following stocks, so they sell out of the market. Either way, the phrase "sell in May and go away" gets passed around once every year. What should you do with your stocks in May?

First, don't sell. As Fool Alex Dumortier demonstrated by analyzing the returns of the S&P 500 (SNPINDEX:^GSPC) from 1926 to 2012, buying and holding returned 1.6% more compared to selling in May and buying back in October. And depending on transaction fees and taxes, the outperformance of "buy and hold" compared to selling in May could be even higher.

Second, if you're still worried, take a look at these defensive stocks that have held up well from Mother's Day to Memorial Day and beyond, and those looking relatively cheap headed into May.

Stalwart stocks
One of the most resilient stocks in tough times is General Mills (NYSE:GIS), maker of Cheerios and other such staples. While the S&P dipped more than 6% last May, General Mills lost only 1.6%. Throughout the Great Recession, when the S&P dropped more than 50%, General Mills took less than a 10% hit. And even with a steady business of cereal, the company doesn't rest on its laurels. Last year it acquired Food Should Taste Good, which brought several organic and natural food brands into the fold; a stake in Yoplait, which gives General Mills a piece of the growing yogurt market; and Brazilian Yoki Alimentos, which increases the company's emerging-market presence.

While General Mills trades at a slight premium to the market based on P/E, it offers a dividend yield of more than 3%, and it might just be worth paying for the quality of the company.

In addition to General Mills, Travelers (NYSE:TRV) represents a stable choice for less stable markets. Last May the company shed less than 3% of its share price, and it outperformed the market by more than 20% between 2007 and 2009. The recent rough weather patterns put a dent in Travelers' earnings, but the company constantly returns value to shareholders through extensive share buybacks, lowering share count an astounding 45% since 2006. Its dividend yield is north of 2%. While multibagger gains aren't likely to be had from this insurance giant, its earnings power and shareholder returns should remain stable.

Undervalued in April
Besides traditional performers, there are some stocks priced quite lucratively heading into May.

The market recently punished Whole Foods Market (NASDAQ:WFM) for a same-store sales increase of only 7% and less optimistic full-year guidance. But this should just be a blip for long-term investors. Management has proved itself competent in a slow economy, having scaled back plans for 400 stores by 2010 in the face of the recession. The company now has 335 stores, with a new goal of 1,000 in the U.S. With astonishingly low debt compared to other grocers (only $25 million versus a cash pile of more than $900 million), the company can move at its own pace, and instead of paying off interest it can reinvest in growth and image. Although you'll pay for the quality of this company, it could well be worth the future returns.

While not a hidden gem, another potential buy is Apple (NASDAQ:AAPL). The company sits on an enormous cash pile of $137 billion, has a talented workforce, and is the company best positioned to continue capturing value from consumer electronics. While PCs wane, Apple's iPad remains a premier tablet, and the iPhone continues to gain market share. Its workforce is also aligned unlike any other competitor. Horace Dediu of Asymco explains:

Apple is a functional organization. Unlike almost every other large company it's not organized in "divisions" which have responsibility for "a business" in the sense of profit or loss. At Apple most people or teams are assigned a function like "design", "engineering", "sales" etc. When a product is being built, they are assigned to that effort. When the product is complete, they go to another product.

Apple has a strong moat through its products, resources, and organization, and it has the ability to reignite interest from investors.

Buying in May
May is just another month, and there are plenty of stocks that will enrich you through May and beyond. Above are just a few ideas.

Fool contributor Dan Newman owns shares of Apple. The Motley Fool recommends Apple and Whole Foods Market. The Motley Fool owns shares of Apple and Whole Foods Market. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.