By Holly Yan, CNN

(CNN) -- The last time Americans faced a fall and winter like this, World War I was just ending.

A months-long pandemic exploded in the fall of 1918, killing 195,000 Americans in just the month of October.

Fast-forward 102 years, and the US is on track for another devastating fall and winter. By the end of December, Covid-19 could kill more than 2,900 people a day in the US, according to projections Monday from the University of Washington's Institute for Health Metrics and Evaluation.

But it doesn't have to be that way. With a smart approach to these cold-weather months, researchers say you can defy their grim projections.

Why is the fall / winter outlook so bad?

Health experts say colder weather, the flu season, reopened schools and pandemic fatigue are a recipe for the most difficult months yet in the fight against coronavirus. Here's why:

Colder weather: When more people gather indoors, there's less opportunity for viral particles to disperse -- increasing the risk of coronavirus spread.

And "there's good enough data to say that aerosol transmission (of coronavirus) does occur," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

Respiratory aerosols are smaller than respiratory droplets and can be emitted when a person talks or breathes.

"Aerosol means the droplets don't drop immediately. They hang around for a period of time," Fauci said.

This becomes "very relevant" when you are indoors and there is poor ventilation.

The flu-coronavirus double whammy: The flu season generally starts in October. And its collision this year with the coronavirus pandemic could deal a significant blow to the health care system -- and your own body.

"You can certainly get both the flu and Covid-19 at the same time, which could be catastrophic to your immune system," said Dr. Adrian Burrowes, a family medicine physician in Florida.

In fact, having one of the two viruses can actually make you more vulnerable to getting infected with the other, said epidemiologist Dr. Seema Yasmin, director of the Stanford Health Communication Initiative.

"Your defenses go down, and it makes you vulnerable to getting a second infection on top of that," Yasmin said.

Getting a flu shot this year may be more important than ever

Outbreaks in schools and on college campuses: Many schools that brought students back to classrooms are suffering with outbreaks that could keep growing in the coming months.

And once students and teachers get infected, they can unknowingly spread the virus in their communities.

Athens-Clarke County, home to the University of Georgia, managed to keep its Covid-19 numbers relatively low throughout the summer but suffered a "dramatic spike" in cases in the community, Mayor Kelly Girtz said.

"Clearly, it's the return to campus of large numbers of students who are not here through the summertime," the mayor said.

Some universities have already canceled spring break due to Covid-19 concerns. Those include Syracuse University, Georgia Tech and Ohio State.

Pandemic fatigue: We're nowhere near herd immunity, and a vaccine probably won't be publicly available until the middle of 2021.

Until then, the daily US death toll is expected to steadily climb through the end of this year, reaching more than 2,900 US deaths a day by December 27, according to the IHME's projections Monday.

There are two main reasons for that projected surge, IHME Director Dr. Christopher Murray said.

"First, as case counts have come down in some states, we tend to see that people become less careful, they tend to have more contact," he said. "But then the most important effect is the seasonality of the virus -- that people go indoors, transmission happens more.

"That's why our model shows the huge surge that we really expect to take off in October and accelerate in November in December."

How do we prevent this fall / winter surge?

Just because the pandemic is still here doesn't mean you can't enjoy the fall and winter.

Stay outside if you can: Everyone should limit their interactions at indoor venues, said Dr. David Aronoff, director of Vanderbilt University Medical Center's Division of Infectious Diseases.

If you do have gatherings, invest in ways to keep them outdoors -- perhaps with a fire pit, a warm coat or a heat lamp, said Dr. Leana Wen, an emergency room physician and visiting professor at George Washington University's Milken Institute School of Public Health.

Wear a mask: Health experts say wearing a face mask with two or more breathable layers is one of the cheapest, easiest and most effective ways of reining in the virus and getting life closer to normal, faster.

Masks can prevent you from exhaling viral particles without your knowledge if you're a non-symptomatic carrier of the virus.

It could also help save tens of thousands of lives, experts say. If 95% of Americans consistently wore masks in public, 100,000 US lives could be saved by January 1, according to the IHME.

And that projected daily death toll of almost 3,000 in late December would drop to about 1,000 if virtually all Americans wore face masks in public.

If you visit friends or family, do it wisely: "We know by now that much of Covid-19's spread is actually driven not by formal settings with strangers but by informal gatherings of family and friends," Wen said. "Some individuals may be letting down their guard with loved ones."

If you must travel for the holidays, cut out risky behavior before your trip, such as dining at restaurants indoors or getting in close contact with people you don't live with.

It's also a good idea to get tested before seeing loved ones. But don't get a false sense of security with negative test results.

"Sometimes there are false negatives, which means you have the disease but the test doesn't detect it," according to Penn Medicine.

"Because it is possible to get a negative result even when you have coronavirus, it is important to be careful even when you receive a negative result."

And even if a negative test result is correct, you may have been infected since that test was taken.

Find fun ways to celebrate the holidays safely: This season doesn't have to be doom and gloom. In fact, the CDC offers a long list of ways to celebrate Halloween and Thanksgiving safely.

Instead of Halloween parties or trick-or-treating, the CDC suggests carving pumpkins with your family or with friends and neighbors, at a safe distance.

You can also have virtual costume contests or a Halloween scavenger hunt, "where children are given lists of Halloween-themed things to look for while they walk outdoors from house to house admiring Halloween decorations at a distance," the CDC said.

For Thanksgiving, you can celebrate by having a virtual dinner with friends or family from afar and sharing your favorite Thanksgiving recipe, the CDC said.

You can also help loved ones who are at high risk for Covid-19 or those who are feeling isolated by preparing traditional Thanksgiving dishes "and delivering them in a way that doesn't involve contact with others."