NEW YORK (CNN/Money) - A key gauge for predicting economic activity rose for the fourth straight month in August, pointing to a further pickup in growth in the second half of the year, a business group said Thursday.

The index of leading indicators rose 0.4 percent to 113.3 last month, the Conference Board said, in line with economists' forecasts. The August reading followed a revised 0.6 percent increase in July.

"The economy is improving, although the road will likely remain bumpy," said Ken Goldstein, an economist at the Conference Board, a New York-based business research group.

The board said the 2.5 percent increase in the leading index since its low in March has already been followed by stronger economic growth in the second quarter.

"In addition, the recent strength in the leading index suggests a further strengthening of economic growth in the second half of the year," the board said.

But the improved outlook was tempered somewhat as a reading of the current business climate showed weakness.