• Stock futures rose Friday, reversing course after a down day.
• Federal Reserve Chair Jerome Powell is speaking at 10 a.m. ET.
• New Covid shots are on the way.

Here are five key things investors need to know to start the trading day:

1. Reversing course

Stock futures rose Friday, reversing course after a down day. The Dow Jones Industrial Average fell 0.4% Thursday, the S&P 500 lost 0.9% Thursday, and the Nasdaq Composite shed 1.7% for its worst day since Aug. 5. The Dow and S&P are clinging onto week-to-date gains with one trading session to go. But the Nasdaq is slightly negative on the week headed into Friday trading. Follow live market updates.

2. Powell speech

Federal Reserve Chair Jerome Powell is speaking at 10 a.m. ET Friday from the Fed's annual gathering of global central bankers in Jackson Hole, Wyoming. With a likely September rate cut on the horizon, Wall Street will be listening more broadly for larger policy comments. In previous speeches at the yearly conclave, Powell has presented his thoughts on traditional unemployment thresholds and introduced more flexible inflation targeting.

3. Home sales

Home sales rose in July for the first time in five months. Closed sales of previously owned homes were up 1.3% over June, the latest indication of an early-stage recovery in the housing market. Lawrence Yun, chief economist for the National Association of Realtors, said that despite the month-over-month gain, sales are still "sluggish." "But consumers are definitely seeing more choices, and affordability is improving due to lower interest rates," Yun said.

4. New boost

New Covid shots are on the way. The Food and Drug Administration on Thursday green-lit updated vaccines from Pfizer and Moderna that better target strains of the virus that are circulating and fueling a summer surge in cases. "Given waning immunity of the population from previous exposure to the virus and from prior vaccination, we strongly encourage those who are eligible to consider receiving an updated COVID-19 vaccine," said Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, in a statement. The updated jabs could be available as soon as the coming days.

5. Robo rideshare

Your Uber ride could soon be driver-free. The ride-hailing giant and General Motors' Cruise autonomous driving unit announced a multi-year partnership to offer driverless rides on Uber's platform as soon as next year. The companies declined to provide specifics around the launch or the terms of their agreement, but Cruise CEO Marc Whitten said in a statement that the tie-up would unlock a "new era of urban mobility." Cruise is in the process of reviving its robotaxi business after an October incident in which a Cruise vehicle dragged a pedestrian 20 feet, causing the company to temporarily cease operations.

– CNBC's Yun Li, Jeff Cox, Diana Olick, Annika Kim Constantino, Lora Kolodny and Michael Wayland contributed to this report.