It’s being called "The Great American Eclipse" and, to cope, the US state of Idaho is suspending all road construction work in the third weekend of August to facilitate hundreds of thousands of expected "eclipse-chasers" eager to glimpse an event that won’t be repeated at that location for 375 years.
On 21 August the New Moon comes fully between the Sun and the Earth, casting parts of Earth into a darkness nearly as complete as night.
On this occasion the moon’s umbra – the darkest part of its shadow – will cut an ominous, narrow path across the whole of the US, with selected sites named by NASA as optimum viewing sites.
One of those on the so-called "path of totality" is the city of Idaho Falls, in the northwestern state of Idaho, and the city has risen to the occasion by putting on duck races, a country music concert and scores of other events to cater for up to 500,000 out-of-state visitors.
The real attraction, though, will be the celestial manoeuvrings, with event boosters promising that observers in Idaho will be treated to a full one minute and 41 seconds of "totality".
As exciting as this is for sky-gazers, it means headaches for highways officials, with the department of transportation warning that the eclipse could impact eastern Idaho’s highway system more than any event in recent history.
For that reason it has decided to suspend construction projects and maintenance on most highways during eclipse weekend. Officials also are developing an incident response plan and identifying potential highway bottlenecks.
"Coordinating will ensure eclipse-chasers are safe, their needs are attended to and traffic flows well," spokesman Bruce King told local newspaper The Post Register.
He added: "The more traffic you have on the state highway system the more potential there is for congestion, and the more congestion there is the more risk of accidents, therefore we want to minimize any impediments to safe travel."
The issue is serious enough that, to get ready, officials are holding monthly planning meetings with law enforcement agencies.
The 21 August total solar eclipse is somewhat unique in that the "path of totality" crosses such a densely populated land mass. Most of the paths hit ocean.
In July 2019 a total eclipse will be visible for a short period in southern South America, as it will again in December 2021. In April 2023 one will cross northern Australia.
Image shows a partial solar eclipse in 2014, Minneapolis (Tomruen/Creative Commons)