(CNN) Millions of low-income Americans could have a harder time affording food if the partial government shutdown continues into February.

Funding for food stamps, school lunches and nutrition for pregnant women and young children is expected to run out next month if the impasse isn't resolved, experts say.

The largest benefit at risk is the Supplemental Nutrition Assistance Program, or SNAP, the formal name for food stamps. Nearly 38.6 million Americans depended on this aid to augment their grocery budgets in September, according to the US Department of Agriculture's latest data.

The agency said last month that the program is funded through January, but it has only $3 billion in reserves to cover February. That's less than two-thirds of food stamps' $4.8 billion cost in September.

What the agency would do next is unknown.

If the $3 billion reserve were distributed evenly, that would translate into a roughly $90 cut for the 19.4 million households that receive an average of $245 a month, according to the left-leaning Center on Budget and Policy Priorities.

"That would put a huge hole in the budget every month for families that have very low incomes and would likely result in severe hardship and hunger," said Dottie Rosenbaum, a senior fellow at the center.

A program that provides food assistance to more than 7 million low-income pregnant women, new mothers and young children is similarly threatened. The Special Supplemental Nutrition Program for Women, Infants, and Children also has federal funding to last only through January, according to the National WIC Association, an advocacy organization. The average cost of a monthly WIC food package is just under $41 per person.

Last week, the agency's Food & Nutrition Service division said it intends to allocate all remaining carryover and unspent funds to state agencies, according to the Rev. Douglas Greenaway, the association's president. Federal officials are working with state agencies to see what other unspent money might be available for reallocation. How much is available and how long the program can continue operating will vary by state, but these actions together would push the cutoff date into February.

"It becomes a make-or-break moment likely in mid-February," Greenaway said.

At that point, it's possible states might not sign up new clients or might stop providing benefits to women who recently gave birth or older children, Greenaway said. They might also provide only one month of benefits, instead of the typical three months.

Child nutrition programs, including school breakfasts and lunches and after-school meals, will continue into February, according to the USDA.

While states partner with the federal government on many food assistance programs, they do not have the funds to cover the federal portion during the shutdown, said James Weill, president of the nonprofit Food Research & Action Center.

The USDA did not respond to requests for comment.

If federal nutrition aid does run dry next month, it will put a big strain on the nation's food banks, which provide groceries to tens of millions of Americans through the federal Emergency Food Assistance Program, donations from the food industry and charitable contributions.

The USDA paid for its shipments through March before the shutdown took effect, said Carrie Calvert, managing director of government relations at Feeding America, the nation's largest domestic hunger-relief organization. However, the federal agency is no longer reimbursing states for storing and distributing the products, which costs $5.3 million a month.

So far, no problems have been reported. But Calvert is concerned that the funds will dry up if the shutdown is prolonged.

Another issue: If low-income Americans stop receiving their food stamps and other benefits, more will turn to food banks for help -- many of which don't have the resources to handle the additional crush of people.

The Capital Area Food Bank, which annually serves half a million people in the Washington metro area through 450 pantries, is already planning to boost its stocks since it expects to see more clients soon -- both federal workers and contractors who are losing their paychecks and low-income residents who are losing their government aid. It's already getting queries from the food pantries and soup kitchens it serves about whether they can get more supplies.

The shutdown comes at a bad time because the food bank typically has less inventory in January and February, since it receives fewer donations after the holiday season ends. The nonprofit agency is talking to grocery and corporate partners to see if they can hold food drives in coming weeks.

"We just need to be able to provide more," said Radha Muthiah, the food bank's CEO.