Investors should strongly consider cutting their stock exposure this coming May Day and parking the proceeds in cash until Halloween.

That advice comes courtesy of a famous piece of Wall Street folklore that is known by the adage 'sell in May and go away.'

Unlike most of the other stories investors tell, however, the historical evidence in favor of this one is surprisingly strong. And deeper drilling into the data suggests there are ways to tweak the approach so that you don't have to dump stocks entirely to capture some of the benefit.

You might also know of the 'sell in May' pattern by its other name, the 'Halloween indicator.' Both refer to the pronouncedtendency for the stock market, on average, to turn in its best returns between Halloween and May Day