Recession signals in the world's largest economy are flashing red again.

Growth in the second quarter slowed to a pace that has typically been followed by a contraction within a year. Household spending fell in June for the third straight month; never in the past five decades has this happened outside of a slump. The Standard & Poor's 500 Index plunged 16.8 percent in 11 days, performance that's occurred only twice since at least 1970 without indicating a downturn.

“With so many red flags, the chances of a recession are rising,” said Jonathan Basile, a senior economist at Credit Suisse in New York. “A lot of the economic indicators are teetering. We've gone very quickly from a slowdown scare to a recession scare.”