The fear that has been hanging over markets for most of August lifted on Wednesday. For how long remains anyone's guess.

The stock market started September with a jolt, turning sharply higher after a pair of encouraging reports on manufacturing sent investors seeking out riskier investments. Prices for the safest assets — Treasurys, gold and the dollar — all fell.

With investors suddenly willing to embrace risk, the Dow Jones industrial average added 255 points, its best day since July 7. All 30 stocks in the Dow closed higher. That marked a sharp break from August, when the market's most widely used index turned in its worst performance for the month in nine years.

Reports of stronger-than-expected manufacturing growth in China and the U.S snapped a run of discouraging data on the economy, including dismal readings on home sales and economic output.

The Institute for Supply Management said manufacturing activity in the U.S. rose in August, in contrast to regional reports from recent weeks that pointed to a slowdown.

"It gives us hope that things may not be as bad as they seem," said Zahid Siddique, an associate portfolio manager at Gabelli Equity Trust Inc.

Analysts cautioned that the gains, like many others the market has seen in recent weeks, could quickly pass. A bad surprise from the Labor Department's monthly report on employment, due out Friday, could send investors back into hiding.

The good news on manufacturing "gives some comfort, but that is only good until the next number," said Darell Krasnoff, managing director at Bel Air Investment Advisors.