A strengthening US dollar is casting a growing shadow over third-quarter earnings season, which is due to kick off Wednesday with an evening report from U.S. aluminum giant Alcoa Inc.

The dollar has risen 7% against major currencies since early May, according to the WSJ Dollar Index. On Tuesday, Germany reported that industrial output declined sharply in August, the latest in a string of weak readings that have helped support recent gains in the US dollar against the euro.