Gov. Andrew Cuomo once billed it the “summer of hell,” and now Long Island Rail Road riders will know just how hot it will be.

The MTA on Monday outlined its long-awaited summer service plan for the LIRR as Amtrak works to rehabilitate the decaying infrastructure of the complex. All told, there will be a 20 percent reduction in train service coming into and out of Penn Station from July 10 to at least Sept. 1.

The agency, advised by a 15-member Penn Station task force, will make up for that reduction by adding 36 extra cars to trains; deploying a network of 200 coach buses; and relying on two ferry routes to get Long Islanders to and from New York. But, unlike New Jersey Transit’s summer plans, the MTA will not be offering reduced fares to inconvenienced LIRR riders.

Veronique “Ronnie” Hakim, the MTA’s acting executive director, urged commuters to take the time now to prepare for the ‘‘difficult and challenging summer” that awaits.

The MTA will take on a “robust” public awareness campaign that will include sending letters to employers that recommend offering commuters alternative work options, like working remotely or odd hours.

“Obviously it’s going to be a long, hot summer,” said Hakim at a news conference in MTA headquarters on Monday. ‘‘We know our customers have had enough.’’

On top of peak hour service interruptions, the MTA plans to cancel trains between 2 a.m. and 4 a.m.

The plan didn’t address calls from commuters, advocates and lawmakers to reduce fares for riders during the service reductions, which are expected to last through most of July and August. New Jersey Transit, which is also reducing service into and out of Penn, is cutting fares by as much as 64% for some affected customers.

‘‘Our focus has been providing charter buses and ferries,’’ Hakim said, when asked why the plan did not include a fare reduction. The MTA has invested in trying to create alternative travel strategies for commuters, she said.

MTA officials said subway service would be bolstered at some locations, where LIRR riders will be able to transfer for free.

“I like to get work done on my way in and I can’t do that if we’re all playing musical chairs during our commute,” said Jeff Stein, 32, from Dix Hills. “There should be fare compensation because [the MTA is] failing to deliver the basic things they provide.”

The mission of the task force empowered to help create the plan became more urgent after Amtrak said recently it will need eight weeks to complete its track renewal project this summer, Hakim said.

Anticipating more vehicular traffic, Gov. Andrew Cuomo has ordered the MTA to complete its bridge and tunnel construction projects by July 8.

Cuomo said the accelerated bridge and tunnel construction schedule is to “ease commutes and provide New Yorkers with peace of mind.”

The governor’s order also means “that all major commuting crossings will be cashless and all lanes will be open during the daytime,” including the remaining work to be done at the Queens-Midtown Tunnel, the Robert F. Kennedy Bridge, the Verrazano-Narrows Bridge and Hugh L. Carey Tunnel.

“Our top priority is ensuring all New Yorkers can get where they need to go as quickly and easily as possible this summer and we’re taking every conceivable step to prepare for Amtrak’s summer of hell,” Cuomo said in a statement.

The plan’s release comes less than 30 days before track work is scheduled to begin July 10 at the Manhattan hub. Commuters and advocates have grown frustrated by a lack of information. The Long Island Rail Road Commuter Council said the MTA could provide more detailed information for riders online.

“The primary question is which riders will bear the burden of reduced service out of Penn Station,” said LIRRCC chairman Mark Epstein. “We understand that this is necessary work and that maintaining service from Penn Station depends upon it being completed. We insist, however, that riders be treated fairly and disruptions to their commutes be kept to the minimum level possible.”

Amtrak’s scheduled infrastructure work is supposed to be completed before Labor Day. But it will neither include repairs to the troubled signal system at Penn nor Superstorm Sandy-damaged East River tunnels.

“I think LIRR riders will reach a boiling point this summer,” said Nicholas Chavez, 28, a Port Washington branch rider from Bayside. “Service is horrendous and is only getting worse.”