The Great American Eclipse is nigh!

Millions are expected to pack the so-called path of totality, or the swath of the United States that will be able to experience the complete solar eclipse.

But, as with any major event, some things might not go according to plan. We’ve compiled a list of what could go wrong, from safety hazards to acts of nature. Plan accordingly.

You could seriously damage your eyes

Looking directly at the sun during the eclipse without proper eyewear would harm your eyes “like a magnifying glass on a leaf,” as one optometrist put it to The Washington Post’s Angela Fritz.

Fritz reports: “Depending on the sky conditions, it only takes about a minute and a half for your eyes to be permanently damaged, and the damage is cumulative, meaning you don’t have to stare at the sun without looking away for it to be harmful — you may just be taking quick glances, but it’s still damaging your eye.”

We are going to keep saying this, and saying this, and saying this: If you plan on viewing the eclipse, you will need to wear protective glasses. Regular sunglasses won’t do.

Looking at the eclipse through your camera won’t necessarily protect your eyes, either. You will need a solar filter if you plan on photographing the eclipse to protect yourself — and the camera. You can learn more about them here.

Speaking of which . . .

You could damage your camera

Just like our eyes, cameras are sensitive to the sun’s powerful rays and could be damaged if you don’t use the proper filters and equipment. The types of gear you’ll need to use varies depending on the type of camera you’ll use to shoot the main event. Nikon has a good guide to photographing eclipses, and YouTube has numerous tutorials to offer.

[How to photograph the eclipse with your smartphone]

It might be cloudy

Clear skies are required to view this celestial event, the first total eclipse to pass solely across the United States in the history of the United States. But, of course, it could all be ruined if Mother Nature declines to play along.

With the path of totality spanning from sea to shining sea, there is a chance that some locations will experience adverse weather conditions.

The Washington Post has calculated which locations are likely to have the best weather for viewing. If you still haven’t made travel plans for the eclipse, we recommend you give it a read before you choose your destination.

There might be fires

The eclipse will first make landfall in Oregon, making the state a prime location for avid spectators. However, Oregon has a bit of a problem: It’s in the midst of wildfire season. There are several burning right now, though it’s unclear whether the smoke will impair views of the eclipse.

In addition to natural variables like dry conditions and lightning causing fires, there’s a worry that careless visitors could spark a blaze.

“With human-caused fires up 10 percent this year, we are hoping to educate and engage with folks to prevent the fires we can,” said Ron Graham of the Oregon Department of Forestry. “Common causes are campfires, tossing a cigarette out a window or even idling a hot vehicle over dry grass. One thing these all have in common is,they are all preventable.”

The department is working to educate eclipse visitors on ways to prevent fires and be prepared for any emergencies. They’ve created a guide to not starting fires and a tool called Know Before You Go, which allows people to find out about the latest restrictions caused by fires.

Graham said the department was also placing firefighting resources such as trucks, aviation and staff around the Path of Totality to address any issues that might come up.

“We really just want to partner with Oregonians and visitors alike to help make the Solar Eclipse memorable for all the right reasons!” Graham said.

There’s going to be a lot of traffic

This being America, many people are expected to hit the road to reach the path of totality. According to calculations made by GreatAmericanEclipse.com, 12.25 million people live inside this ribbon of land. They estimate an additional 1.85 million to 7.4 million people will travel to the path of totality to see the event.

“These millions of Americans will produce predictable traffic congestion,” Michael Zieler wrote at GreatAmericanEclipse.com. Areas that aren’t used to floods of humans are expecting numerous visitors — and the congestion that will come with them.

[Interactive: Travel the path of the solar eclipse]

For example, Grand Teton National Park in Wyoming is expecting unprecedented numbers of people pouring in.

“We anticipate it to be the busiest day in the history of Grand Teton National Park,” said spokesperson Denise Germann. They expect ”congestion and traffic gridlock. We’re trying to communicate that to our visitors to create a realistic expectation,” she said.

Germann urged visitors to plan ahead. The park set up a website dedicated to solely to eclipse information.

Grand Teton is making extensive preparations. The park has added numerous viewing spots where people can stop to watch the eclipse. It’s waiving its entrance fee to move people along faster and turning some roads into one-way routes so that viewers can park to watch. Extra staff members will be brought on to cope with the crowds. Afterward, visitors will be encouraged to stick around the park to allow traffic to thin out.

Despite the potential mayhem, the park is eager to host the event. “We’re excited about it. This is a once-in-a-lifetime opportunity for many of us,” Germann said.

Read More:

Video: How do scientists know when and where an eclipse will happen?

Interactive: See how many eclipses will happen in your lifetime

A guide to watching the solar eclipse in the Washington area

Airfares to solar eclipse destinations skyrocket to astronomical levels

Basic facts about our sun and moon that you’re embarrassed to admit you don’t know