You've probably heard of the "January Effect," the phenomenon that seemingly causes stocks, particularly small caps, to surge in the first month of the year. In theory, investors and institutions sell securities in December for tax-harvesting reasons and then buy them back the following month. As a result, the stocks jump in price.

Yet what about other months? Retailers, for example, have some seasons that perform better than others, simply because of the nature of the business. Some stocks even do better in April.

Whatever the reason, investing based solely on the calendar is not a Foolish strategy. Back-testing and data-mining can turn up nearly any causal relationship we want, if we search hard enough. Still, wouldn't it be great to know ahead of time which stocks performed best at what times?

On Motley Fool CAPS, more than 98,000 investors have weighed in more than 5,600 stocks, awarding five-star ratings to the companies that most command their confidence. We've paired their opinions with data going as far back as five years to see which stocks perform best in each month. The following five companies seem to do best in April:

Stock

Market Cap

Avg. % Return, April

Avg. % Return, Rest of Year

CAPS Rating (Out of 5)

YTD Return

Superior Energy Services (NYSE: SPN)

$3.59 billion

12.70%

1.05%

*****

29.14%

Weatherford International (NYSE: WFT)

$27.36 billion

6.41%

2.22%

*****

17.27%

JB Hunt (Nasdaq: JBHT)

$3.98 billion

8.74%

2.43%

**

16.28%

Baker Hughes (NYSE: BHI)

$25.89 billion

6.60%

1.29%

*****

3.39%

USG (NYSE: USG)

$3.52 billion

17.60%

4.36%

****

(0.70%)

Sources: America Online, Yahoo! Finance, and Motley Fool CAPS.

What's driven the stellar April performance of oil-services company Weatherford, even as much of the rest of its year tends more toward sour than sweet and light? Fellow oil-services company Baker Hughes also does well in April, but Halliburton (NYSE: HAL) enjoys its gusher times in January. That's why we don't recommend using this as a list of stocks to buy or sell -- just a platform for further research. Whatever the reason, Weatherford's five-star CAPS rating suggests that investors are drilling deep on this stock.

Except for a few days here and there, the year has been off to an ugly start for many stocks. Most of the companies on our list have been doing well so far, but if April really is their month to shine, let's see which ones seem most likely to live up to the promise.

Weathering the competition
Weatherford recently turned in a quarterly result that beat analyst expectations and showed that its geographic dispersal allowed it to offset the weakness being experienced in the North American market. The erosion of the North American segment affected BJ Services' (NYSE: BJS) results this week as well.

Now that we're in a period of high oil prices, companies servicing the oil industry should reap a windfall. As a result, companies such as Weatherford seem well-positioned to weather the effects that such prices could have on the economy. CAPS player Sly2Slim saw back in January that the oil companies need to invest in the equipment Weatherford provides to maintain their levels of profitability:

With the world slowly realizing that it's fundamentals that are driving oil markets and not speculation (demand [outstripping] supply and heavy draw downs on reserves), oil services look poised to have another robust year. After all, the oil majors need to find new reserves while also replacing declining production from existing oil fields, which is no small task. It will demand an astronomical level of investment, which is where the oil services companies come in, and [Weatherford] appears perfectly positioned to reap the rewards of this windfall.

A calming effect
Have we heard from you? At Motley Fool CAPS, every investor's opinion counts. Your voice affects these stocks, whatever month the calendar may display. Since it's free to sign up and express your investing opinions, why not use this opportunity to take your star turn?

USG is a recommendation of Motley Fool Inside Value. You can shower profits on your portfolio any time of the year with a 30-day free trial subscription.

Fool contributor Rich Duprey owns shares of USG but has no financial position in any of the other stocks mentioned in this article. You can see his holdings. The Motley Fool has a disclosure policy.