A low-volatility environment that took hold of the markets over the past few months truly ended over the last week.

Stocks made dramatic swings during the past five days, as speculation over the outcome of the Federal Reserve's September meeting hit a fevered pitch.

Despite all of the big moves, benchmark indexes closed the week with just slight gains. Over the past five days, the S&P 500 added 0.4%, and the Dow Jones Industrial Average rose 0.2%. The Nasdaq closed 2% higher, boosted by Apple's (AAPL - Get Report) big gains throughout the week. Before last Friday, the S&P 500 had not moved more than 1% in any direction for 44 consecutive sessions.

"The speculation regarding what the Fed may, or may not, do is what's dominating the market," said John Conlon, CIO and chief equity strategist at People's United Wealth Management. "Fed action -- or lack of action -- is almost anticlimactic. Right now, speculation has more life than action, or lack of action itself. This is what's leading the parade, and it's not going to go away."

The likelihood of a September rate hike from the Fed ebbed and flowed for much of the week, depending on who spoke when and what data had just been released. By week's end, investors were fairly confident the central bank wouldn't make its move until the end of the year, at the earliest. Retail sales, producer prices and industrial production in August each came in weaker than expected, reducing the chances the Fed will feel confident enough in the state of the U.S. economy to raise rates next week.

The central bank should be cautious in raising rates too quickly, Federal Reserve Gov. Lael Brainard said in a heavily scrutinized speech to the Chicago Council on Global Affairs on Monday afternoon. Brainard said soft inflation and economic uncertainty requires "prudence in the removal of policy accommodation."

"I believe this approach has served us well in recent months, helping to support continued gains in employment and progress on inflation," she said in prepared remarks. The cautious comments come as a relief to a market churning with uncertainty over the Fed's timeline.

Brainard's "remarks suggest that the Fed is more than comfortable remaining on the sidelines next week," said David Tulk, head of global macro strategy at TD Securities. "The characteristics of the 'new normal' emphasize that patience is warranted, and that the case [for] preemptive policy action is less compelling. If the Fed were considering a move next week, they would likely want to get the market closer to being onside and one would expect a less dovish assessment of the outlook."

The chances of a rate hike in September sit at 15%, according to CME Group fed funds futures. Most analysts are betting on a December hike which has a 45% likelihood.

Members of the Federal Open Market Committee will convene on Tuesday morning for their two-day meeting, culminating in an announcement on Wednesday afternoon. Fed Chair Janet Yellen will also hold a press conference on Wednesday.

Crude oil had a rough week, falling just over 6% and settling at a five-week low. Oil has been under pressure, particularly this week, with little relief to U.S. stockpiles and fading hopes of a production freeze agreement when Organization of Petroleum Exporting Countries informally meet later this month.

On Friday, the latest data showed the number of active oil rigs in the U.S. climb over the past week. Weekly data from Baker Hughes showed the number of oil rigs climb by 2 to 416, its 11th increase in 12 weeks.

Earlier in the week, the International Energy Agency said global demand growth was slowing by more than previously thought. The energy watchdog predicted the slowdown would continue in 2017. And, a monthly report from OPEC out on Monday showed non-OPEC supply for next year revised to a higher level, an indication of ballooning supply in 2017. 

Apple was the biggest winner of the week, gaining 11% over the past five sessions. Shares of the world's largest company rallied on confirmation that initial quantities of its iPhone 7 Plus have sold out globally. The strong preorder performance is comforting to investors worried after two quarters of declining smartphone sales.

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Oracle (ORCL - Get Report) was the only company of note to report earnings in the past week. The software company missed analysts' estimates on its top- and bottom-lines. Oracle's investments in cloud technology paid off, though, with revenue in the unit climbing 59% to $969 million.