Direct answer: U.S. flags are currently at half-mast (half-staff) to honor the death or memorial of a notable public figure, typically a former president, vice president, governor, or other prominent leaders. The specific date range and scope (federal, state, or local buildings) are set by presidential or gubernatorial proclamation and can vary by jurisdiction. What typically drives half-staff declarations

• National level: The president can order the U.S. flag to fly at half-staff to mark national mourning for a former president, service member casualties, or other significant national events. These orders apply to federal properties and often influence state and local practices as well.
• State level: Governors can order half-staff for state buildings within their state to honor local or national figures or in response to events affecting the state.
• Intervals: Flags may be lowered for a specific period (e.g., a few days) or through a designated sunset or interment date, depending on the proclamation.

If you want the exact reason and dates for today (or a specific date), I can look up the current proclamations and summarize who is being honored and for how long.