And while there are plenty of upsides to the natural phenomemon—a late summer tourist boom, a new chocolate-glazed Krispy Kreme doughnut, and a burgeoning interest in astronomy—there’s a potential dark side that has nothing to do with the moon blocking the sun’s light.

Here’s what to watch out for:

Traffic nightmares

Certain areas of 14 states will be plunged into total darkness during the totality of the eclipse, which has the Federal Highway Administration a little concerned. During the 1918 eclipse, there were only 6.1 million cars on the road; today there are more than 263 million—and the eclipse is expected to cross 29 interstate highway routes.

Officials say not to trust your automatic headlights and to expect gridlock. And—hopefully, this goes without saying—don’t try to look at the eclipse while you drive.

Multi-million dollar productivity losses

The more complete the eclipse, the more tempted workers are going to be to abandon their duties and go take a peek. Outplacement company Challenger Gray & Christmas says that’s going to mean a $694 million productivity hit for employers.

Using information from the U.S. Bureau of Labor Statistics, the firm predicts that roughly 87 million people will be working when the eclipse hits. Each of those will spend about 20 minutes watching the event. With an average hourly wage of $23.86 an hour, the typical employee will cost his or her employer $7.95. Multiply that by 87 million and you get that eye-popping dollar figure.

Power issues

Solar energy is increasingly big: installations have increased ninefold since 2012. This year’s eclipse is expected to result in more than 9,000 megawatts of solar power going down—the equivalent of roughly nine nuclear reactors. However, power companies say they’ll tap into alternate methods like gas generators and hydroelectric dams to make up that loss and the North American Electric Reliability Corporation says doesn’t foresee any reliability issues.

Price gouging

The laws of supply and demand always work against people who wait until the last minute. As a result, if you’re just starting your search for eclipse glasses now, you’re probably going to pay a premium for them. Since July 31, the price of a 10-pack of glasses from Soluna on Amazon (AMZN) has climbed more than 4,200%. Of course, this is one area you might want to overpay since the alternative is…

Blindness

Astronomers, optometrists, and ophthalmologists have been warning people for months not to look at the eclipse without the right protective eyewear, but some people are bound to ignored that advice. A safe pair of solar eclipse glasses should be labeled with ISO 12312-2, an international safety standard that indicates the glasses reduce visible sunlight to safe levels and block UV and IR radiation.

And, again, the laws of supply and demand have created a market that’s ripe for exploitation. There are several reports of counterfeits on the market and some organizations that have handed out free pairs are issuing recalls. To be safe, check this list of reputable vendors from the American Astronomical Society.

Lizardmen!

Sure, it’s unlikely, but South Carolina’s Emergency Management Division, in an Aug. 9 tongue-in-cheek tweet, noted that it “does not know if Lizardmen become more active during a solar eclipse, but we advise that residents of Lee and Sumter counties should remain ever vigilant.”