John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
NASA has crunched the numbers on probable cloud cover and revealed the best places to watch the August 21 cosmic spectacle.
The path that the total solar eclipse will make over the U.S. this month is well known: a band running from Oregon through the Midwest into South Carolina. What’s not yet known, though, is whether the weather gods will royally screw eclipse fans by filling the heavens with dense, sun-snuffing clouds.
But never fear, eclipse-watchers: The folks at NASA’s Earth Observatory have your backs with two new visualizations showing how clear the atmosphere will likely be on August 21. The space agency blended satellite data from 2000 to 2016 to paint a representation of average cloud cover for that date, showing areas historically flooded with clouds in white and those prone to blue skies in blue.
A brief takeaway: If you’re planning on taking in the eclipse in Tennessee or the Carolinas, you might want to maximize your odds by diverting hundreds or thousands of miles to Idaho, Wyoming, and Oregon.
It often seems that saying it’s going to rain one day is a great way to guarantee absolutely spotless skies. But at least this visualization clarifies your odds of seeing the only total eclipse to pass exclusively through the U.S. since 1257. (Look for the agency’s follow-up forecast when the next one occurs in 2316.) And NASA is doubling down with another map identifying cities with a historically better chance of cloudless skies in darker blue and those often victim to summertime scud-and-such in lighter blue.
If you want to catch the eclipse in a proper city, book it to Salem, Oregon; Idaho Falls, Idaho; or Casper, Wyoming. Other towns in the path of the band of totality, though perhaps with greater chances of it being behind clouds, are Lincoln, Nebraska; Jefferson City, Missouri; St. Louis, Missouri; Nashville; and Columbia and Charleston, South Carolina. Of course, a partial eclipse will be visible outside the totality band, and places that can spot this phenomenon in good weather are represented on the map as progressively smaller polygons.
If you want to know what drives cloudiness during this time of month, the space agency provides this explanation:
The likelihood of clouds is higher in the eastern portion of the country because the position of the Bermuda High regularly steers warm, humid air over the eastern, southern, and central United States in August. Meanwhile, the Cascade Range in western Oregon and Washington forces moist air upward and triggers rainfall as air flows over the mountains. This produces a stark rain shadow that keeps the western parts of these states wet and cloudy and the eastern parts dry and clear.