With ridership creeping up to its highest levels since the pandemic began, the MBTA will boost frequency on its subway system and more than two dozen bus routes next month, officials announced Monday.

A new summer schedule that takes effect on June 20 will run Red, Orange and Blue Line trains at close to the same frequency they did in the winter before a package of unpopular service cuts hit, plus deploy more Green Line trolleys on the C, D and E branches.

The T will also boost midday frequency on the Red and Orange Lines to a level even higher than before the cuts took effect, with headways of six minutes on the Red Line trunk and 7.5 minutes on the Orange Line. That change is driven by a COVID-era shift in which typical rush hours have been less crowded and other times of day have been busier.

Roughly 30 bus routes will also run with greater frequency starting June 20. As previously announced, that target date will also feature restoration of four other bus lines that had been eliminated in the spring service cuts: the Route 18 through Dorchester, the Route 52 from Dedham to Watertown, the Route 55 from the Fenway neighborhood to Copley Square and the Route 68 from Harvard Square to Kendall Square.

The frequency changes are scheduled to arrive five days after Gov. Charlie Baker lifts the COVID-19 state of emergency on June 15.

MBTA officials in December narrowly approved a package of service cuts trimming frequency 20 percent on the Red, Orange and Green Lines and non-essential bus routes and 5 percent on the Blue Line and essential bus routes, responding to a pandemic-fueled sharp decline in travel and fare revenue.

After facing significant criticism and receiving nearly $2 billion in federal emergency aid, T higher-ups pledged in March to reverse the cuts and restore pre-COVID levels across the system “as soon as possible.”

The increased bus frequency coming to about 30 routes means that the T will not have as much flexibility in its scheduling, MBTA Deputy General Manager Jeff Gonneville said. The agency, which has been scrambling to hire enough workers to run pre-pandemic levels of service, will need to reallocate drivers who in recent months have been available to supplement more crowded routes as needed.

Ridership remains well below past norms, but it continues to trend upward.

MBTA General Manager Steve Poftak said Monday that the T carried more riders during the week of May 10, the most recent span with data available, than it has in any week since COVID-19 hit.