Ahead of the return of "The Flash" on March 17, The CW has announced the season finale dates for both it and its sister show, "Arrow."

The final episode of the first season of "The Flash" is slated for May 19 at 8PM. "Arrow's Season Three finale airs a week earlier on Wednesday, May 13.

Yesterday, the return of "The Flash" was heralded by an all-new poster featuring star Grant Gustin in an unusually relaxed pose.

The next episode, "Out of Time," is set to feature Liam McIntyre guest-starring as another one of the Flash's famous rogues -- Mark Mardon, The Weather Wizard; the show's second version of the villain. "The Flash" airs Tuesdays at 8 p.m. on The CW. Here's the official episode description of "Out of Time":

LIAM MCINTYRE GUEST STARS AS THE WEATHER WIZARD; CISCO REALIZES DR. WELLS IS HIDING SOMETHING - Mark Mardon aka The Weather Wizard (guest star Liam McIntyre) appears in Central City intent on avenging his brother Clyde's death, and sets his sights on Joe (Jesse L. Martin), who shot Clyde. When Mardon attacks Joe and Barry (Grant Gustin), Barry is able to super-speed them to safety but Mardon gets away. Barry warns Joe not to go after a meta-human alone but Joe doesn't listen and ends up in grave danger. Meanwhile, Cisco (Carlos Valdes) looks into the night the team captured the Reverse Flash and realizes something doesn't add up and begins to wonder whether Joe was right about Dr. Wells (Tom Cavanagh). Barry and Linda (guest star Malese Jow) end up on an awkward double date with Eddie (Rick Cosnett) and Iris (Candice Patton). Thor Freudenthal directed the episode written by Todd Helbing & Aaron Helbing (#115). Original airdate 3/17/2015.