“Sell in May and go away” may be a catchy phrase that makes the rounds every year, but it comes with more risks than rewards for those investors who may be tempted to try to time the market.

“If you say to yourself, ‘I know the markets are going to be better or less expensive in November,’ then you’re making a market call,” said Adrian Mastracci, a portfolio manager and financial adviser at KCM Wealth Management in Vancouver.

“If you can live and die by market calls, that’s wonderful. But all the studies I’ve seen have said that the changes in your portfolio returns are really due to asset mix.”

The maxim comes from the idea that stocks do better sometime between November and April than during the summer lull, when a low liquidity period and fewer transactions may create more volatility.

But that’s not always the case.

“Right now, world markets are improving and the market returns for the U.S. and international markets are picking up steam,” said Sadiq Adatia, chief investment officer with Sun Life Global Investments.

“If you were to miss out and not participate in the markets from May to September, you could potentially lose five per cent of your portfolio value because you are sitting on the sidelines.”

And while trying to guess how the market will perform may pay off once in a while, the probability of getting it right is low and it’s a gamble that comes with more question marks than you may realize.

“You have no idea what’s going to happen that day you decide to pull to market or pull out of the markets,” Adatia said.

Before the 2008 financial crisis, the markets weren’t bad from May to September, but if you came back in September, you got “the worse possible scenario,” he said.

Christopher Stewart, a financial adviser with Edward Jones in Halifax, notes that if someone had invested $10,000 in 1976, by 2012 that investment would have risen to $122,709, a 7.2 per cent annual rate of return.

But if the investor missed the 10 best days in the stock market over that 37 year period, the amount would have dropped to $63,032, a 5.2 per cent average annualized rate of return.

“Missing the best days can be costly,” Stewart said. “You have no way of knowing when they will be; they could be right smack in the middle of August. Sometimes they are.”

He advises his clients to avoid trying to guess what markets will do and instead focus on the things they can control: their plan, the quality of their investments, the diversification of their portfolio and their time frame.

“If someone was really concerned about this, that would be a big clue to me that we should at least have a discussion about their risk tolerance,” he said.

If you’re not interested in simply buying stock and holding it for an extended period of time, Adatia suggests slowly trimming your position and lowering the equity content of your portfolio as the valuations get more expensive.

“Look at the market conditions and determine whether or not you want to take some off the table or add some,” Adatia said.

“It should never be all or nothing. You can’t get that right. But adjusting slowly, given all the information you see, is very much doable.”

To Mastracci, the fees and commissions you’ll have to pay when you sell and buy back in are another reason to treat the summer as business as usual.

Deferred sales charges fees may apply when you sell mutual funds, or you may owe tax on capital gains when you sell your current investments.

“Instead of selling in May, set your asset mix,” he said. “Trim some of the leaders and add to some of the laggards that you’ve got in the portfolio (and) relate everything you do to the target mix that you set for yourself.

“It’s a form of rebalancing.”