This story has been updated.

The world’s longest international border has reopened to American travelers: On Aug. 9, Canada started welcoming back tourists from the United States, making them the first nonessential travelers to set foot in the country since the pandemic began.

For some Americans, such as Sherry Marlan, reopening allows not only a return to sightseeing, but also a reunification with family. On Tuesday, Marlan will be traveling to Victoria, B.C., to see her daughter and grandchildren for the first time in more than a year and a half.

“I cannot wait to have my arms around them again,” she said. “I am so excited.”

Americans can feel relatively safe upon getting to Canada, which has one of the highest-vaccinated populations in the world. More than 80 percent of people 12 and older have received at least one dose, and more than 68 percent are fully vaccinated.

The Canadian hospitality industry has spent this summer gearing up for the return of American travelers, who have historically fueled the majority of tourism in the country.

“Canadian businesses are excited and ready to welcome back our U.S. friends and family,” said Liz Sperandeo, a spokesperson for Destination Canada. “The travel industry has invested billions in health and hygiene protocols, retraining staff and reconfiguring experiences to prepare for visitors.”

If you’re looking to take a trip to the Great White North this summer, here’s what experts say you need to know before packing your bags.

The hyper-transmissible delta variant of the coronavirus has left would-be travelers uncertain. The Post spoke to an expert about how to safely make that call. (The Washington Post)

How to get there

To board a flight to Canada, Americans must present both proof of full vaccination and a negative molecular coronavirus test (such as a PCR test) taken within 72 hours of their scheduled departure time.

Make sure you don’t cut it close with that 72-hour timing — you could end up paying a bunch for a replacement test if yours is invalid by even 10 minutes. Daryl Silver, president of Continental Travel Group, said having a paper copy of your test results is “really, really helpful,” as gate agents will want to review it before giving you your boarding pass. And after his own recent trip to Canada, Silver recommended obtaining and showing gate agents a physical boarding pass, too.

Two other essentials are your original proof of vaccinations and the ArriveCAN app, to which travelers must upload photographic proof up to 72 hours before departure. ArriveCAN will also have travelers answer questions to make the customs process easier, as well as create a backup plan in the event they are not approved for Canada’s quarantine exemption.

The app “is very straightforward, very simple and easy to use,” Silver said.

If crossing by land, vaccinated travelers will have to present their documentation and a negative result taken within 72 hours before arrival at the border, or proof of a positive coronavirus test taken between 14 and 180 days before arrival.

Unvaccinated travelers arriving by land are allowed, but have to quarantine and take a test on day 8. More info can be found here.

What to know about restrictions

Once you cross through the Canadian border, there may be one last thing you have to do before your vacation begins: get tested (again). Canada is currently randomly testing vaccinated travelers who arrive by land and air. You may be tested on site, or given a a self-test and submit your results within 24 hours. You can find more info here.

If the test comes back negative, you are free to go about your trip as planned — although the Canadian government asks that you keep a record of all close contacts within the first 14 days. If you test positive for the coronavirus, or start showing symptoms, you will need to quarantine for 14 days in the location you detailed in your ArriveCan quarantine plan. On the eighth day, you will then be required to take another coronavirus test, which you must pass to leave quarantine.

Canadian Transport Minister Omar Alghabra announced that vaccinations will be required starting this fall for all passengers on planes, cruise ships and interprovincial trains. Most restaurants and events do not currently require proof of vaccination, but check ahead of time so you can avoid any complications.

Masks, meanwhile, are mandatory in some Canadian provinces, although restrictions vary depending on the region. Even in areas where masks are not mandated, they are encouraged indoors and at large gatherings.

How to dine and explore

Canada’s vast natural landscapes — from the Rocky Mountains to the Maritimes — make for beautiful sites for camping or a day trip. In its cities, take advantage of the lovely new patio areas along the streets for drinks and dining. While restaurant, museum and tour reservations are a must in many places around Europe and the United States, travelers will have a much easier time being spontaneous in Canada, experts said.

One thing you shouldn’t play by ear? Car rentals. Like the United States, Canada is facing a car rental shortage, since many companies sold off their fleets during the pandemic. Book your rental car several weeks in advance to snag one before they sell out.

Sperandeo, of Destination Canada, said American tourism will be critical to Canada’s economic recovery from the pandemic. Historically, Americans have made up 68 percent of international overnight visitors to the country, and Destination Canada forecasts that they will make up 54 percent of total international tourism over the next four years.

Jeff Doane, Accor hotel group’s chief commercial officer for North and Central America, said many Canadian hotels are ready and waiting for American tourists.

“The great thing about Canada is that it has a population of California and it’s bigger than the United States, so there’s a lot of great outdoors out there,” Doane said. “It’s a great place to go out and explore.”

Where to get a coronavirus test before returning home

As with their flights to Canada, American travelers will need to present a fresh negative test before boarding the plane home.

Information about where you can find tests can be found on the U.S. Embassy website. Another option is to pack an at-home test before your departure. You take these tests over a video call with a health-care professional.

Most major airports in Canada have resources on where to get tested in or near the airport, so do your research to find the best price and location for you. The tests can be quite expensive, running anywhere from $120 to $250, depending on the testing site and how far in advance you book. You can also pack an at-home test that you can take before you leave.

According to Marc Atchison, editor in chief of TraveLife magazine, many Canadians are cautious about the border’s reopening, which comes as the delta variant is surging and the United States remains closed to Canadian tourists.

But “overall,” he said, “I think Canadians will be very glad to see our American cousins. It will be a sure sign that normal times are returning.”