'Chicago Fire', 'Chicago Med', 'Chicago PD' Threeway Crossover Night Announced

The three Chicago universes will converge this fall.

On Wednesday night, Chicago Fire co-creator Derek Haas took to Twitter to officially announce the highly anticipated Chicago Fire, Chicago Med, and Chicago P.D. three-way crossover, also revealing to fans that it will happen much sooner than expected.

Fire into Med into PD for one night only. pic.twitter.com/Pqr1GyjMVY

— Derek Haas (@derekhaas) August 15, 2018

"BREAKING NEWS: our second episode of the season is going to be a three way crossover with Chicago Fire leading the way," Haas wrote. "Fire into Med into PD for one night only."

All three Chicago series premiere Wednesday, Sept. 26 starting at 8/7c on NBC, which puts the One Chicago crossover event on the following week's schedule, airing on Oct. 3.

The popular NBC dramas were renewed for additional seasons by the peacock network in May, with the official announcement coming just ahead of Chicago P.D.'s season finale. Each series celebrated the news on Twitter, sharing celebratory messages with fans.

"The ED isn't closing its doors yet! Chicago Med will be back for Season 4," the official Chicago Med account tweeted at the time.

"In the words of Stella Kidd, this story is FAR from over. Chicago Fire returns for Season 7 on NBC," Chicago Fire's Twitter account celebrated.

"The 21st isn't going anywhere," Chicago P.D.'s official account announced. "Chicago P.D. is returning for Season 6."

Of the three series, Chicago Fire is the lowest rated, though it still manages to draw in an average of just under than 6 million viewers per episode and a 1.1 rating in the key 18-49 demographic. Meanwhile, medical drama Chicago Med reigns supreme among the Chicago universes, with an average audience size of 6.7 million viewers and a 1.2 rating. Chicago P.D. draws an average of 6.4 million viewers and a 1.2 rating key demo rating.

The Once Chicago three-way crossover event will likely see ratings that surpass all of the series' averages.

The crossover will see the casts of the three series converge, including Chicago Med stars Nick Gehlfuss, Yaya DaCosta, Colin Donnell, Brian Tee, Torrey DeVitto, and Oliver Platt, Chicago Fire's Jesse Spencer, Taylor Kinney, Eamonn Walker, Monica Raymund, and David Eigenberg, and Chicago P.D.'s Jason Beghe, Jon Seda, Jesse Lee Soffer, Patrick John Flueger, and Elias Koteas. However, it is not yet known if all of the series' stars will make appearances in the epic event.

Chicago Med, Chicago Fire, and Chicago P.D. all premiere Wednesday, Sept. 26 starting at 8 p.m. ET on NBC.