Law enforcement agencies will be out in force this Labor Day weekend, on the lookout for intoxicated drivers and boaters as Long Islanders head outside for summer’s unofficial grand finale.

Suffolk and Nassau police will increase patrols on the streets and the waterways, courtesy of state grant money set aside for such enforcement.

“It’s that one last weekend to really enjoy the summer, to go out and have a good time with your families,” Suffolk County Executive Steve Bellone said Thursday. “But we also know that when you have a weekend like this and people are celebrating and partying and having a great time, there’s also the greater risk of injury and people being hurt or killed in accidents.”

Suffolk Police Commissioner Timothy Sini urged residents to “be considerate, make smart decisions” and arrange a ride home, if necessary.

Sini noted that Suffolk police made 45 arrests of drunken and impaired drivers during the holiday weekend last year.

“Drunk drivers and boaters put the lives and safety of innocent people in jeopardy every time they get behind the wheel,” Nassau County Executive Edward Mangano said in a statement.

There were 54 DWI arrests in Nassau over last year’s Labor Day weekend.

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Gov. Andrew M. Cuomo said State Police and law enforcement agencies throughout the state will participate in the national “Drive Sober or Get Pulled Over” DWI campaign.

“Drivers can expect to see sobriety checkpoints during the campaign, along with more troopers on major highways during this detail,” the governor’s office said in a news release. “In addition to the DWI checkpoints and patrols, Troopers will also be watching for distracted or impaired drivers, vehicle occupants who are not properly buckled up, and drivers that are violating the Move Over Law.”

Millions in the metropolitan area will hit the roads and rails and take to the air this holiday weekend.

The Port Authority said it expects about 7 million people to use its airports, bridges and tunnels.

Travelers using LaGuardia Airport should remember it is in its first year of a decadelong reconstruction that has snarled traffic on airport roads — and sometimes back onto the Grand Central Parkway.

“LaGuardia Airport travelers are urged to allow extra time and use mass transit,” the Port Authority said. “Check with the airlines in advance to ensure flights are departing and arriving on schedule.”

To encourage the use of mass transit this weekend, the Port Authority and the Metropolitan Transportation Authority are offering free LaGuardia Link Q70 bus service, in effect at 12:01 a.m., Friday until 11:59 p.m. Monday.

The LaGuardia Link provides nonstop service that connects the airport’s main terminals with the subway and Long Island Rail Road transit hubs in Jackson Heights and Woodside, Queens.

The LIRR said it will have eight additional trains departing Penn Station between 1:49 and 3:48 p.m. Friday. Those trains will run to Babylon, Far Rockaway, Huntington and Ronkonkoma.

There will be one additional train to Montauk, beginning at Jamaica after taking on passengers from trains originating at Penn Station and Atlantic Terminal.

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On the roads, the state said it will halt nonemergency road work between Friday and Tuesday mornings to accommodate motorists.