866,734 people have voted so far.

Election Day is Tuesday, November 3, 2020. Montana allows any voter to request a ballot by mail. You can also vote in person. Montana offers early voting.
Vote in person
Vote on Election Day
Voters registered in Montana can look up where to vote on Montana's site.
Vote early
Montana voters can also vote before Election Day through a process called absentee in-person voting. The period for absentee in-person voting runs from Monday, October 5, 2020 to Monday, November 2, 2020, but dates and hours may vary based on where you live.

What to bring
You will be asked to show ID to vote in Montana. Acceptable forms include: a current photo ID showing your name; or a current utility bill, bank statement, paycheck, voter registration confirmation, government check or other government document showing your current name and address.
Voters without ID: If you are unable to provide ID, you can still vote by requesting and filling out a "Polling Place Elector ID" form. Or, you can vote a provisional ballot. Your provisional ballot will be counted if you provide one of the items on the list to the county election office by 5:00 p.m. the day after the election, or mail it to the county election office postmarked by the day after the election.

Based on the 238 million voting-eligible Americans this year and slightly higher self-reporting of voter enthusiasm, I’d go with 65% turnout - or 155 million ballots cast. That would be up from 60% turnout in 2016 and the highest turnout in decades.