New York City's primary day is finally here.

Polls opened at 6 a.m. on Tuesday, Sept. 12, and are set to close at 9 p.m. in districts throughout the five boroughs. Only voters who are registered with a political party can vote on the ballots.

Polling locations can be found online, including on the city’s Board of Elections website, or by calling 866-868-3692.

State Attorney General Eric Schneiderman’s office has a hotline for anyone who experiences problems at the polls during the day, 1-800-771-7755. Voters can also email their complaints to his office at civil.rights@ag.ny.gov.

This year’s New York City primary elections may not have the drama of previous contests, but there are still plenty of reasons why voters should pay attention and head to the polls.

All 51 seats on the New York City Council are up for election. And there is no incumbent running for 10 of those seats.

Seven seats will be vacated by council members who must step down at the end of 2017 due to term limits. Two others, Julissa Ferreras-Copeland, of Queens, and David Greenfield, of Brooklyn, decided not to pursue another term. And Queens Councilman Ruben Wills is no longer in the running after being convicted on corruption charges.

These open seats paved the way for a flurry of contenders and even a Republican primary in Brooklyn – a political rarity in a city dominated by Democratic voters.

Since City Council races usually hinge on a small number of voters, upsets are always a possibility.

“When you have low turnout, that means you have people who are hardcore supporters for one candidate,” said Christina Greer, an associate professor of political science at Fordham University. “There are a lot of people who still aren’t thinking about elections in September.”

Here are some races to watch:

District 4 – Manhattan

Covers a large swath of the Upper East Side and midtown including Yorkville, Times Square, Peter Cooper Village and Stuyvesant Town, Turtle Bay, Tudor City and Sutton Place.

This is one of the city’s most crowded primaries with nine Democrats hoping to take the seat held by City Councilman Daniel Garodnick, who is leaving due to term limits.

The candidates include Vanessa Aronson, a former public school teacher and diplomat; Maria Castro, a community activist; Alec Hartman, the CEO of TechDay; Rachel Honig, a marketing agency owner; Jeffrey Mailman, the counsel and legislative director to City Councilwoman Elizabeth Crowley; Keith Powers, a former legislative aide and lobbyist; Bessie Schachter, a former aide to State Sen. Liz Krueger; Barry Shapiro, a retired business systems analyst and Marti Speranza, a community activist and small business owner.

Affordable housing, school overcrowding and transit access are key issues in this race.

Powers has received key media endorsements along with union backing from 1199 SEIU and the support of city Comptroller Scott Stringer. He released a detailed 22-point plan to improve city government. But Speranza boasts the largest campaign war chest of the candidates and the vital United Federation of Teachers endorsement.

District 21 – Queens

Includes the neighborhoods of East Elmhurst, Elmhurst, Jackson Heights and Corona.

City Councilwoman Julissa Ferreras-Copeland decided not to run for re-election setting off one of the uglier local contests this year.

Former state senator and city councilman Hiram Monserrate is making yet another comeback attempt. The disgraced former lawmaker was convicted of misdemeanor assault on his girlfriend in 2009 and pushed out of the Senate. In 2012, he was convicted of mail fraud, and he has since served almost two years in jail.

He is facing off against Francisco Moya, a state assemblyman who has the backing of Gov. Andrew Cuomo, City Council members, unions and Ferreras-Copeland. In a recent debate televised on NY1, Moya likened Monserrate’s latest bid for office to “a bank robber applying to be a bank teller.”

Monserrate insists he has reformed and still has a dedicated group of supporters in the neighborhoods he once represented.

The redevelopment of Willets Point, affordable housing and overcrowded schools are key issues in this district.

“I’ve learned from my mistakes,” Monserrate said during the NY1 debate. “I’ve paid my price.”

District 43 – Brooklyn

Includes Bay Ridge, Dyker Heights, Bensonhurst, Bath Beach.

A total of nine Democrats and Republicans are eyeing the seat, which is up for grabs because term limits will not allow City Councilman Vincent Gentile to run for re-election.

Gentile is a Democrat, but voters in those neighborhoods have elected Republicans in the past. This is the only Council seat in the city that will have both a Republican and Democratic primary.

Democratic candidates include Justin Brannan, Gentile’s former chief of staff; Kevin Carroll, an aide to Councilman Stephen Levin; Vincent Chirico, an attorney; Khader El-Yateem, a pastor and Nancy Tong, an aide to Assemb. William Colton.

Michael Bistreich, a former Gentile aide who is suing the councilman for allegedly discriminating against him because he is autistic, has publicly accused Brannan of participating in the harassment. Brannan has denied the allegations.

The Republican candidates include: Robert Capano, a business manager and former political aide; Liam McCabe, political consultant and former aide to U.S. Rep. Dan Donovan; John Quaglione, chief of staff to State Sen. Marty Golden and Lucretia Regina-Potter, a design consultant.

Transportation, especially involving the R subway line, is a big concern in this district along with illegal home conversions and more funding for local schools.

District 9 – Manhattan

Includes Central Harlem, Morningside Heights, Upper West Side, East Harlem.

City Councilman Bill Perkins is running for the second time this year for his seat. A former state senator, Perkins served in the City Council representing the Harlem area from 1998 to 2005. He left Albany for City Hall when former Councilwoman Inez Dickens vacated the seat after winning a special election for the Assembly earlier this year.

This elaborate game of musical chairs is not unusual in the political world, but Greer finds it troubling.

“Under term limits you can only be in the City Council for eight years, but then you can leave and come back again,” she said. “I’m really uncomfortable with these Albany-City Hall swaps.”

Perkins is facing five Democrats including Marvin Holland, the political and legislative director for Transport Workers Union Local 100, who came in second place in the last special election.

Other contenders include: Cordell Cleare, former chief of staff to Perkins; Tyson-Lord J. Gray, an attorney; Julius Tajiddin, a community activist and Marvin Spruill, a salesman and actor.

The candidates have focused on how to create more affordable housing, improve local schools and concerns about gentrification.

District 38 – Brooklyn

Includes Red Hook, Sunset Park, Windsor Terrace.

City Councilman Carlos Menchaca won this seat in 2013 by defeating incumbent Sara Gonzalez, who was known for her poor attendance rate and introducing few pieces of legislation while in office.

Menchaca made history as the first Mexican-American elected to public office in the city and the first openly gay Council member from Brooklyn.

But Gonzalez is looking to reclaim her seat. She is just one of the primary challengers Menchaca is facing.

State Assemb. Felix Ortiz is running for the seat, along with attorneys Chris Miao and Delvis Valdes. Ortiz has some big union endorsements such as 1199 SEIU, the United Federation of Teachers and the Patrolmen’s Benevolent Association.

Menchaca has the backing of Congress members Nydia Velazquez and Jerold Nadler and several of his City Council colleagues as well as DC 37, 32BJ and the Transport Workers Union.

Menchaca was a driving force behind the creation of the IDNYC municipal ID card available to all New Yorkers, including undocumented immigrants.

While Menchaca has been praised for his efforts on immigrant issues, Ortiz has criticized what he said is a lack of constituent services.

Here are some of the other Primary Day races you shoud know about. Republican candidates in the races below are running unopposed:

Mayor - Democrats 

Bill de Blasio, incumbent

Sal Albanese

Robert Gangi

Richard Bashner

Mike Tolkin

Collin Slattery

Joel Rodriguez

Public Advocate - Democrats

Letitia James, incumbent

David Eisenbach

Bronx borough president - Democrats

Ruben Diaz Jr., incumbent

Camella Pinkney-Price

Brooklyn district attorney - Democrats

Eric Gonzalez, acting incumbent

Patricia Gatling

Anne Swern

Vincent Gentile

Stephanie Ama-Dwimoh

Marc Fliedner