“The invasive nature of restoration efforts” prompted the decision to close immediately for safety reasons, St. Michael’s rector Fr. Michael Busch said in a statement. St. Michael’s had originally planned to close later in the summer, but safety is the first priority, Busch said.

Restoration has been underway for the past three years.

A complete closure of the cathedral will run from now to mid-December. A brief Christmas season opening will be followed by full closure from January to March next year. Open for Holy Week and Easter, St. Michael’s will then remain open until September, with the restoration scheduled to be complete for the Sept. 29 Feast of St. Michael, patron of the archdiocese.

Throughout the restoration St. John’s Chapel will continue to offer daily Mass, accessible from 200 Church St.

St. Michael’s Choir School will shift its Sunday Mass schedule in July to nearby St. Paul’s Basilica, beginning in July. St. Paul’s will add extra weekend Masses.

The cathedral is also urging its parishioners to seek Sunday Masses at other downtown parishes, including St. Basil’s on the campus of the University of St. Michael’s College just off Bay Street, north of Wellesley and St. Mary’s, where Adelaide meets Bathurst Street.

St. Paul’s Sunday Masses are on Saturday at 4:30 p.m., Sunday 8:30 a.m. and 11 a.m. In July the basilica will add Masses at 6 p.m. Saturday, 9:30 a.m. Sundays and 1 p.m. Sundays.

St. Basil’s weekend schedule begins with the Mass of anticipation Saturday at 5 p.m. Sunday morning Masses at 9 a.m., 10:30 a.m., noon and 4:30 p.m.

St. Mary’s Mass schedule features English-language Masses at 5 p.m. Saturday and 11:30 a.m. Sunday. Portuguese-language Masses are Sundays at 8:30 a.m. and 10 a.m.