* Yellen appears before Congressional committee at 10:00 a.m. ET
* Tempur Sealy drops on disappointing forecast
* Indexes up: Dow 0.22 pct, S&P 0.14 pct, Nasdaq 0.1 pct (Updates to open)
By Yashaswini Swamynathan
Sept 28 (Reuters) - Wall Street rose on Wednesday, helped by higher oil prices and gains in financial stocks ahead of Federal Reserve Chair Janet Yellen's testimony before a Congressional committee.
Yellen's testimony will be watched for clues on the timing of the next interest rate hike, a week after the central bank held rates steady but suggested that a move could come later this year.
Minneapolis Fed President Neel Kashkari said the central bank could keep rates low for a while as inflation remains weak.
Investors are also awaiting comments from Fed officials including voting members Esther George, James Bullard and Loretta Mester, who will be speaking at separate events.
The S&P 500 financial sector was up 0.22 percent and gave the biggest boost to the benchmark index, while energy rose the most by 0.7 percent, driven by higher oil prices.
Stocks, which have rallied in the absence of an interest rate hike this year, are highly sensitive to Fed comments due to a lack of consensus among officials on the timing of future increases.
"I don't expect a major shift in Fed rhetoric, which is to make hawkish comments, but follow with dovish action," said Adam Sarhan, chief executive at Sarhan Capital.
"Unless Yellen or one of the other Fed heads go way off reservation and make a statement, I don't expect massive fireworks today."
At 9:42 a.m. EDT the Dow Jones industrial average was up 39.86 points, or 0.22 percent, at 18,268.16.
The S&P 500 was up 3.04 points, or 0.14 percent, at 2,162.97.
The Nasdaq Composite was up 5.48 points, or 0.1 percent, at 5,311.20.
Nine of the 11 major S&P 500 indexes were higher.
Mattress maker Tempur Sealy's shares plunged 21.8 percent after the company forecast disappointing full-year sales.
Nike dropped 1.6 percent after the shoemaker's future orders missed analysts' estimates for the third time in a row, attracting a slew of price targets by brokerages.
Wells Fargo rose 0.72 percent, following its statement that CEO John Stumpf would forfeit unvested equity awards worth about $41 million and will not get a salary while the board investigates its sales practices.
Advancing issues outnumbered decliners on the NYSE by 1,955 to 687. On the Nasdaq, 1,379 issues rose and 814 fell.
The S&P 500 index showed nine new 52-week highs and one new lows, while the Nasdaq recorded 40 new highs and six new lows. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Anil D'Silva)