Effective Sunday Oct. 3^rd , U.S. Postal Service priority flat rate prices and first-class package prices will be raised. This increase is mainly due to the approaching holiday season. These price increase will not impact single-piece first-class mail (which is smaller and lightweight) that is travelling in the same region or international mail.

These changes are part of  the new 10-year plan to achieve financial sustainablity and service excellence  announced by Postmaster General Louis DeJoy on March 23. The "new service standards" that are part of the plan are aimed at improving service reliablility and increasing efficiency accross the Postal Service network.  

Other changes included in the plan are a goal of six and seven days of mail and package delivery, a target of 95% on time reliability (currently at 83.6%), a new electric delivery fleet, and a goal to reduce turnover by 50%, among other targets. A full PDF and a brief overview of the plan can be found here.