10 things you need to know before the opening bell

Here is what you need to know.

The Dow suffers its 3rd-biggest one-day point drop in history. The Dow Jones industrial average tanked 831 points, or 3.15%, on Wednesday as traders grappled with global growth concerns, trade fears, and the possibility of more Fed rate hikes.

Global markets are getting pounded. China's Shanghai Composite plunged 5.2% and Britain's FTSE is down 1.76%. Dow futures are showing a drop of more than 330 points at the open.

Trump rails against the Fed over rate hikes. "I think the Fed is making a mistake," Trump told reporters before a campaign rally on Wednesday. "They are so tight. I think the Fed has gone crazy."

The market is doing something rarely seen over the past 20 years - and it could mean the meltdown is just getting started. Stocks and bonds have been battered in recent days and their negative correlation means there could be further pressure ahead, according to Jim Paulsen, the chief investment strategist at Leuthold Group.

Bitcoin tanks as cryptocurrencies join in global market bloodbath. The number one cryptocurrency by market capitalization plunged as much as 7%, to a low of $6080.99 a coin, before slightly paring its losses.

Elon Musk denies report that James Murdoch is the top choice to replace him as Tesla's chairman. "This is incorrect," Musk tweeted in response to a story from the Financial Times saying Murdoch was the "lead candidate" to replace him atop Tesla's board.

Altria is reportedly in talks to buy a stake in a Canadian cannabis producer. The maker of Marlboro cigarettes is reportedly talking to the Canadian cannabis producer Alphria about a taking a minority stake, the Canadian newspaper The Globe & Mail reports. Alphria shares jumped more than 16% Wednesday, following the news.

Hurricane Michael weakens to a tropical storm. Michael made landfall in the Florida panhandle as the strongest hurricane to hit the US in nearly 50 years, and is now a tropical storm as it makes its way across Georgia.

Earnings reports trickle out. Delta Air Lines and Walgreens Boot Alliance report ahead of the opening bell.

US economic data flows. CPI and initial claims will both be released at 8:30 a.m. ET. The US 10-year yield is little changed at 3.16%.