What to Watch on Tuesday: J-Lo, Taylor Swift perform at American Music Awards

American Music Awards (8 p.m., ABC) - The 2018 awards show will have performances from Jennifer Lopez, Taylor Swift, Carrie Underwood, Imagine Dragons, Post Malone and Ty Dolla $ign. The show is hosted by Tracee Ellis Ross.

The Flash (8 p.m., The CW) - In the Season 5 premiere, an unexpected guest from the future appears at their home, and Barry and Iris must figure out how to get her back to the future without disrupting the timeline.

Black Lightning (9 p.m., The CW) - The board considers a motion to shut down the school in the Season opener, forcing Jefferson to go to Napier Frank to sway the vote.

The Circus (9 p.m., PBS / UNC-TV) - Part 2 of the American Experience documentary about the rise and fall of the traveling tented railroad circus.

Some programming details are provided by networks.