On Monday, around 450,000 people are expected to head to Dallas, the largest city in Texas in the path of totality for the total solar eclipse. The phenomenon—where the moon completely obstructs the sun as it orbits the Earth—is alternately rare and common.
A total solar eclipse actually happens once every year and a half or so. “However, at any given location, it may be several centuries between occurrences,” the National Weather Service says.
The most recent total eclipse in north or central Texas was in 1878. This area won’t get another until 2317. The NWS says that Hearne, in Robertson County, isn’t in the path this year and won’t be until 2343. The last one the town saw was in 1286, which means more than 1,000 years will have elapsed since the last. That can help explain why the city of Dallas is expecting so many visitors.
The eclipse will begin around 12:23 p.m. and last until a little after 3 p.m. Totality should last from about 1:40 p.m. to 1:44 p.m., per NASA’s estimates.
But there is this tricky matter of the weather. Pretty much every meteorologist in Texas agrees that we’re going to get clouds and storms on Monday. But the type of clouds, and when they are likely to settle above us, is still being sorted out. So far, it seems that thin, high clouds will be in place Monday morning, and there’s a good chance they’ll increase in density throughout the morning. This means we could have a great deal of cloud cover by the time the eclipse starts at 12:23 p.m.
But there could be breaks in the clouds during the prime viewing time—the whole process will take about three hours, even if totality lasts just four minutes.