The moon’s shadow cones during a total solar eclipse. Observers on Earth
within the smaller, central shadow, or umbra, see a total eclipse. Within the larger shadow, the
penumbra, observers see a partial eclipse. Credit: NASA

The all-American total solar eclipse is still two months away, but federal and state agencies are already getting the word out about how eclipse-chasers can keep safe and sane.

It’s been 99 years since the last total solar eclipse swept across America from coast to coast, so there’s little precedent available for modern-day planning. But the Department of Transportation is predicting that on Aug. 21, the day of the eclipse, interstate highways in the path of totality could be flooded with many more drivers than the 2 million people per day who typically travel those routes.

The big message? Be prepared.

“It’s not a time to just show up on the spur of the moment … not a time to just pull off on the side of the road,” Martin Knopp, associate administrator for operations at the Federal Highway Administration, said today during a pre-eclipse news briefing organized by NASA.

Eclipse traffic projection
This map projects how busy traffic will be along the track of totality on Aug. 21, the date of the solar eclipse. The color scale goes from an easygoing green to jammed-up red. (Google Maps)

Knopp said that drivers should be watchful on the roads, not only for other drivers, but for pedestrians as well. “We lose too many lives on the highways already,” he said.

The biggest hot spots are likely to include Nashville, Tenn., the largest city in the direct path of totality; and central Oregon, which is currently projected to have the highest chance of clear skies.

It’s way too early to predict the weather for Aug. 21. But the National Oceanic and Atmospheric Administration, which owns and operates the nation’s weather satellites, says historical records hint at a higher chance of cloudiness along the coasts, and a progressively higher chance of clouds as the inland track of totality goes from east to west.

That points to three central Oregon counties – Deschutes, Jefferson and Crook – as ground zero for eclipse-chasers. Peter Murphy, a spokesman for the Oregon Department of Transportation, said officials are planning for 1 million visitors to the state on Aug. 21, and 250,000 visitors to the tri-county area. That influx would double the area’s population, he noted.

“It’s like two Woodstocks in the state, and three Rose Bowls at one time in our area,” he said.

Weather projection for eclipse
This map projects the chances of cloudiness along Aug. 21’s track of totality, based on historical data. Darker circles denote a higher chance of clouds in late August. It’s too early for an actual weather forecast, however. (NOAA Graphic)

To keep traffic moving, Oregon DOT will station crews at strategic spots along Highways 97, 26 and 20 on eclipse day, Murphy said. The agency is planning to use websites, social-media accounts and its TripCheck and 511 mobile services to update travelers on road conditions, based on data harvested from cell phones.

Murphy said travelers should try to settle in one place for Aug. 21. “We’re asking people to arrive early and plan on staying for a while,” he said. “We don’t want ‘day-of’ travel. We’re really urging people not to do that.”

Here are a few tips for planning eclipse travel:

  • Check the weather forecast a couple of days ahead, and plan your eclipse-chasing strategy accordingly.
  • Many road construction crews will be stopping work on eclipse day, but that doesn’t mean the work zones are going away. Expect delays.
  • Stock up on food and water for the trip, and plan your bathroom breaks as well. “People need to know where they’re going to ‘go’ along the way,” Murphy said.
  • Don’t plan on pulling over to the side of the road to watch the eclipse. And definitely don’t try looking at the sun while driving.
  • The path of totality crosses 20 national parks, which could serve as great destinations for travel. But  again, plan ahead.
  • Turn on your headlights for totality.

The safety measures shouldn’t stop after getting out of the car at your viewing location. Don’t gaze at the sun during the partial phase of the eclipse unless you’re wearing eye protection. You should take off your eclipse glasses if the sun is completely covered, but put them back on when totality ends.

Read more: 3 things you should do for the solar eclipse

Millions of eclipse glasses will be distributed through public libraries and organizations such as Astronomers Without Borders. You can also buy the glasses online or at stores. If you have young children, practice using the glasses in advance so they’re ready for the big day.

You can also download a free educational guide to the eclipse, courtesy of the Moore Foundation and the Space Science Institute.

For those who are unable to reserve a hotel room or a campsite for Aug. 21, or those wanting to avoid the traffic altogether, NASA will be streaming live video of the total solar eclipse from 10:15 to 11:45 a.m. PT on that day. It’s all part of a campaign called “Eclipse Across America: Through the Eyes of NASA.”

Like what you're reading? Subscribe to GeekWire's free newsletters to catch every headline

Job Listings on GeekWork

Find more jobs on GeekWork. Employers, post a job here.