Dollar weakens as Tropical Storm Harvey rages

While the euro extended Friday's gains against the dollar, the U.S. currency also slipped against the yen, dipping 0.1 percent to 109.23 yen.

The dollar index – which tracks the U.S. currency against six major rivals – fell to as low as 92.372, its weakest since early May 2016, before recovering a little to trade 0.3 percent down at about 92.489. 

Those declines came after Fed chief Yellen focused more on financial stability in her Jackson Hole speech. 

The remarks disappointed some investors who had hoped for hints on the Fed's plans for interest rates, though most analysts had not expected Yellen or Draghi to shed new light on policies. 

"Draghi does not seem to be overly concerned with the current euro levels, which is the market's justification to move the euro higher," said Commerzbank currency strategist Esther Reichelt.