The late night tweet from Lancashire MP that hinted at leadership challenge to come
Mr Evans, a member of the influential Conservative 1922 backbench committee, tweeted at 11.53pm last night that he would be making "no comment on events taking place later today".
Mr Evans tweeted: "As an officer of the 1922 I will be making no comments on events taking place later today. All communications will be made by The Chair of the Committee Sir Graham Brady."
A result is expected an hour after the vote takes place.
She has also warned that a change in leadership would derail or delay Brexit.
1922 Committee Chairman Sir Graham Brady said he spoke with Theresa May last night to inform her that the threshold had been reached and a leadership ballot would take place.
"The Prime Minister was very keen that the process should be concluded as quickly as reasonably possible," he told reporters on Wednesday morning.
"She will come at 5 o'clock this afternoon to speak to colleagues in the 1922 committee and then we will conduct the ballot immediately after that, between 6 and 8 o'clock, with a result announced as quickly as we are able.
"It was clear she was keen to have resolution. She wanted to have this process concluded as quickly as possible. I think you can take it she was keen to get on with business."