[13] The county has a humid continental climate which is hot-summer (Dfa) except in higher areas to the north where it is warm-summer (Dfb).

The landscape of Passaic County, near the north edge of New Jersey, spans some hilly areas and has dozens of lakes.

The highest point is any one of six areas on Bearfort Ridge in West Milford at approximately 1,480 feet (450 m) above sea level.

The southeastern, more populous half of the county is either flat, along the Passaic and Pompton Rivers, or mildly hilly, among the Watchung Mountains.

The Commissioners also appoint individuals to departments, agencies, boards, and commissions for the effective administration of the county government.

[26][27] As of 2025[update], Passaic County's Commissioners are (with terms for Chair and Vice-Chair ending every December 31):[24][28][29][30][31][32] Republicans have not won countywide office since 2021.

Nicolino Gallo's 2021 third-place finish for the three Board seats at stake then represents the first time any Republicans have been in the county government since now-State Senator Kristin Corrado left her position as County Clerk to win that seat in 2017, as well as the first time the Board has had any Republican members at all since 2012, when then-Freeholders Deborah E. Ciambrone, Michael Marrotta, and Edward O'Connell were defeated.

[40] In March 2023, the commission swore Orlando Cruz, the president of the Greater Paterson Chamber of Commerce (as well as its counterpart in neighboring Wayne), into office to replace retiring commissioner T.J. Best, who resigned at the beginning of the month to spend time with family members down in Georgia.

[52][53] For the 119th United States Congress, New Jersey's 5th congressional district is represented by Josh Gottheimer (D, Wyckoff).

[54][55] For the 119th United States Congress, New Jersey's 9th congressional district is represented by Nellie Pou (D, North Haledon)[56] For the 119th United States Congress, New Jersey's 11th congressional district is represented by Mikie Sherrill (D, Montclair).

Aura Dunn (R) Jay Webber (R) Alixon Collazos-Gill (D) Benjie E. Wimberly (D) Clinton Calabrese (D) Christopher DePhillips (R) In 2004, the New Jersey Legislature passed the Highlands Water Protection and Planning Act, which regulates the New Jersey Highlands region.

The northwestern area of the county, comprising the municipalities of Bloomingdale, Pompton Lakes, Ringwood, Wanaque and West Milford, was included in the highlands preservation area and is subject to the rules of the act and the Highlands Water Protection and Planning Council, a division of the New Jersey Department of Environmental Protection.

[59] Some of the territory in the protected region is classified as being in the highlands preservation area, and thus subject to additional rules.

All of the incorporated municipalities within the county also have separate local police departments, almost always exclusively providing law enforcement operations within their physical boundaries.

In January 2024, Sheriff Richard Berdnik committed suicide inside a Turkish restaurant.

[61] Passaic County has a number of NJ Transit stations, including Montclair State University, Little Falls, Wayne/Route 23, and Mountain View on the Montclair-Boonton Line.

The “Main Line” corridor also runs through the county and includes the following stations: Hawthorne, Paterson, Clifton, Passaic, and Delawanna.

Route 19 runs entirely through the county, connecting the Garden State Parkway with Interstate 80 and Paterson.

Since 1996, the county has leaned Democratic until recently, as Republicans have made significant gains in the country, especially in the more urban parts.

In the 2016 presidential election, Democratic support declined to 59.5%, although nominee Hillary Clinton still won the county comfortably overall, and the 2020 presidential election saw Democratic support decline to 57.5% - a margin of 16.5% for former Vice President Joe Biden over Republican President Donald Trump, which was a slightly wider margin than the state as a whole.

Most of these areas are census-designated places (CDPs) that have been created by the United States Census Bureau for enumeration purposes within a Township.

The Bureau of Economic Analysis calculated that the county's gross domestic product was $20.5 billion in 2021, which was ranked 13th in the state and was a 4.8% increase from the prior year.