10 things you need to know before the opening bell

Janet Yellen's Humphrey Hawkins testimony begins. Fed Chair Janet Yellen's semi-annual Humphrey Hawkins testimony begins before the Senate Banking Committee at 2 p.m. ET. In her testimony, expect Yellen to discuss the US labor market, inflation, and the impact of a possible Brexit, among other things. The testimony continues on Wednesday before the House Finance Services Committee.

Remain is surging the polls. The latest poll from The Telegraph shows Remain has jumped out to a 7 point lead. The poll, conducted by ORB International, shows Remain ahead of Leave by a 53% to 46% margin. The British pound is up 0.3% at 1.4736, and at its highest level since January 4.

George Soros says a Brexit would cause the pound to crash. Billionaire George Soros warned a Brexit would lead the British pound to a bigger collapse than seen on Black Wednesday, the day the Bank of England took the pound off the European Exchange Rate Mechanism. According to Soros, a Brexit would cause a drop of at least 15% and possibly more than 20%. Soros is known as "the man who broke the Bank of England" by placing a massive bet against the currency ahead of Black Wednesday.

Germany's highest court backed the ECB's OMTs. The German Constitutional Court tossed out five lawsuits challenging the validity of the European Central Bank's Outright Monetary Transactions program, which was the centerpiece of Mario Draghi's promise to do "whatever it takes" to save the euro. Bloomberg reports, the judges ruled "Germany's government institutions, including the Bundesbank, must monitor the implementation and review whether the OMT program keeps these limits once it is put in action." The OMT program has never been used.

Germany's ZEW sentiment surged past estimates. The ZEW Indicator of Economic Sentiment for Germany rose to 19.2 in June. The number was up from May's reading of 6.4 and well ahead of the 5.1 that economists were expecting. "The improvement of economic sentiment indicates that the financial market experts have confidence in the resilience of the German economy," said ZEW president professor Achim Wambach. "However, general economic conditions remain challenging. Apart from the weak global economic dynamics, it is mainly the EU referendum in Great Britain which causes uncertainty."

Dell is selling its software business. Three people familiar with the matter told Reuters that Francisco Partners and the private equity arm of activist hedge fund Elliott Management are teaming up to buy Dell's software unit for more than $2 billion. The sale comes as Dell looks to get rid of all of its software assets as it tries to shore up its balance sheet following its $67 billion purchase of EMC back in October.

There might be a buyer of some Sports Authority stores. New York City-based Modell's Sporting Goods and British-based Sports Direct are considering a joint bid for as many as 200 stores of bankruptcy retailer Sports Authority, Reuters reports, citing the Wall Street Journal. Bidding for Sports Authority's leases concludes on Tuesday, the report says.

Stock markets around the world are mostly up. France's CAC (+0.7%) paces the gains in Europe after Japan's Nikkei (+1.3%) led in Asia. S&P 500 futures are up 10.25 points at 2084.50.

Earnings reports trickle out. CarMax and Lennar will report ahead of the opening bell while Adobe Systems, FedEx, and KB Home release their quarterly results after markets close.

Data remains absent. It picks back up again on Wednesday with the release of the FHFA Housing Price Index and existing home sales.