The fourth season began airing on October 10, 2017, and is set to run for 23 episodes on The CW until May 22, 2018.

Answer this question: when does the flash season four come out? Let's give stream of consciousness first:
The important part for answering this question is: The fourth season began airing on October 10, 2017, and is set to run for 23 episodes on The CW until May 22, 2018.
So, the final answer is October 10 , 2017.