Here's what to know if a partial government shutdown goes into effect

Congress is scrambling to lock in a plan to keep several key government agencies funded before a Friday deadline -- or risk a partial government shutdown that, among having other impacts, could eventually affect food assistance for millions.

Funding for the agencies -- about 20% of the government -- would run out on Friday night, and one week later on March 8, funding for the other 80% of government agencies also would expire if Congress fails to act.

Here's what to know about what would happen if a partial shutdown takes effect at the end of the day March 1.

Which agencies would be affected in the shutdown?

If Congress can't strike a deal, funding for the departments of Agriculture; Energy, Transportation, Housing and Urban Development and Veterans Affairs, including military construction, would expire Friday night.

Medicare, Medicaid and Social Security payments wouldn't be affected in a shutdown. Neither would the U.S. Postal Service, which uses its own revenue stream.

What happens to workers during a shutdown?

A shutdown means workers at those agencies who aren't deemed essential would have to stop working and would be furloughed. Employees in essential roles would be required to keep working without pay.

Many government employees would be told to report to work without pay, including service members, air traffic controllers and inspectors for railroads and airports.

More than 100,000 workers are expected to be furloughed on the spot without a solution from Congress by Friday night.

What about food assistance programs?

Two major food assistance programs under the Department of Agriculture could be affected by a long-term shutdown.

The Special Supplemental Food Program for Women, Infants and Children -- known as WIC -- helps feed nearly 7 million at-risk, low-income women, infants and toddlers and is funded through March under the current continuing resolution. Funding won't dry up right away, but an enrollment surge of about 400,000 last year could mean wait lists increase if funding stays flat.

The Supplemental Nutrition Assistance Program -- also known as SNAP -- had an average monthly participation of approximately 42 million individuals in 2023. The USDA acted to ensure that SNAP participants will get their March assistance.

Veterans' benefits will still be available

Government agencies have contingency plans in place should a shutdown occur -- some involve furloughs or reduction of services.

With Veterans Affairs, about 17,800 employees would be furloughed and about 441,000 would be retained and paid thanks to advanced appropriations.

Veterans' medical care would still be available in the event of a shutdown. Other benefits would continue to be processed and delivered, including compensation, pension, education and housing benefits.

In a news conferences Monday, VA Secretary Denis McDonough said there would be "no impact on veteran health care" if a shutdown were to happen.

"However, we would not be able to conduct most outreach to veterans. Our public-facing regional offices would be closed and many regular operations like career counseling, transition assistance, and cemetery ground maintenance would not be available," McDonough said.

How would transportation be affected?

Key transportation operations would continue in a shutdown, but some services and employees would be affected.

Roughly 16,600 of the more than 45,000 Federal Aviation Administration employees are expected to be furloughed in a shutdown, agency officials said. Another 400 Federal Railroad Administration employees are expected to be furloughed.

TSA officers would continue to work without pay. However, with potentially fewer on duty, the White House has warned of possible longer wait times for travelers, as was the case in previous shutdowns.

Services such as facility security inspections under the FAA and research and development under the railroad administration would halt.

Rental assistance not immediately at risk

Rental assistance programs -- which serve 4.5 million households -- would not be immediately affected by a shutdown since they are funded through April, said HUD deputy press secretary Zachary Nosanchuk.

A shutdown would "greatly delay" the distribution of HUD grants to communities across the country, "possibly causing problems for counties, cities, and towns," Nosanchuk said. New grant funds would not be available in a shutdown, he added.

Haven't we been here before?

We sure have. This is the fourth time since October that Congress has stared down a government-funding deadline. Congress has already passed legislation to buy itself more time to negotiate long-term funding bills on three separate occasions since then.

But each passing deadline ups the stakes. Ukraine aid, border security provisions, and Kevin McCarthy's speakership have all been casualties of previous government funding standoffs.

ABC News' Allison Pecorin and Sam Sweeney contributed to this report.