When Does Indicator-Watching Become Voodoo Investing?

Can your weatherman tell you when stocks are overbought?

Female hand drawing positive graph on the panel with financial statistics

[In Pictures: The S&P's 10 Worst Trading Days]

Unless you know a good reason to defy the eternal laws of mean reversion, this might be a good time to stop digging yourself into a fixed-income hole. "Bonds are a very crowded trade," says Detrick. "Yields are at generational lows. That's not the best time to put money into bonds."

But stocks? What if the rain theorists are on to something? Lakewood's McClellan says you can't be too sure. "What's happening is that the Federal Reserve and quantitative easing are stomping all over natural fluctuations," he says. "Whether that is good or bad is a different question."