A time has not officially been set by Downing Street, but Mr Johnson is expected to address the nation from his new £2.6 million TV studio at around 5pm.
Not only had India's rocketing coronavirus rate seen the country record more than 150,000 new cases a day for three weeks, but the UK is concerned about a Covid strain first identified there which has since been found in Britain.
Experts are currently investigating the B.1.617 variant to see whether it is more transmissible, deadly, or can evade vaccines.
It is possible the press conference could reveal the investigation's findings.
Mr Johnson will face questions on why the government did not act sooner to cancel his trip and restrict travel, given experts have been concerned for weeks about the situation there.
There'll also be questions on why India is not being added to the red list immediately, rather than 4am on Friday.
From Friday, arrivals from India will have to quarantine in a hotel for 10 days before being allowed into society, but up to that point people will be able to self-isolate.
There are fears people carrying the Indian variant could pass it on to others when travelling from the airport to the place they will self-isolate.
Listen to the ITV News Politics Podcast:
The prime minister is also certain to speak about the newly-proposed, fiercely opposed, European Super League, which would see football teams break away from their national leagues to join with Europe's richest clubs.
Mr Johnson, who has vowed to block the breakaway league, will host a round table with representatives from football governing bodies including the FA and the Premier League as well as fans’ representatives before leading the press conference.
The prime minister promised football fans prior to Tuesday’s meeting he will do everything possible to give the “ludicrous” new league a “straight red”.The experts joining the PM at the press conference have not yet been revealed.