Weather Whys March 26, 2015

Courtesy Texas A&M

Q: I see that a few weeks ago, it was proved that there was snow on the ground in all 50 states. Has there ever been a day when it was sunny all over the United States?
A: The short answer is probably no, but no one really knows for sure, says Brent McRoberts of Texas A&M University. Modern weather records only go back about 100 years, so if there were cloudless days in the U.S. before then, it would not have been recorded. “This very question has been asked before,” he says. “The National Center for Atmospheric Research has some of the top weather people in the world, and their best guess is that it’s probably impossible for the entire U.S. to have a cloudless day. Modern satellite images have been in use since the early 1970s and they provide us with the best overall pictures of the U.S., but the best answer appears to be a ‘no.’ “

Q: Why are there no cloudless days over the U.S.?
A: The sheer size of the country is one reason. With more land mass, there’s a greater chance that someplace you will have some clouds and storms, McRoberts adds. “But adding to that is a constant flow of weather systems moving across the U.S., and these almost always have clouds somehow associated with them. This applies to the continental U.S., but especially is true with Alaska and Hawaii, where either rain or snow is almost a daily occurrence, and of course, you won’t have sunny days in those conditions. So it’s safe to say that somewhere in the U.S. at any given time, there are storms of some type, meaning the chance of a cloudless day across America is probably near zero.”