In one respect, we’re all pretty much always under the weather by default of living beneath the atmosphere. But that might not be the most welcome response when someone tells you they’re under the weather—meaning they don’t feel well.
While people generally agree that the idiom has nautical origins, it’s not entirely clear what those origins are. One popular theory posits that ailing sailors recuperated belowdecks, putting them literally under the weather decks (those exposed to the elements). An offshoot of that explanation claims that crewmen and passengers would go belowdecks during bad weather in order to forestall seasickness.
But there are a couple notable holes in this line of thinking.
All Aboard the Struggle Bus (Or Boat)
First of all, although a ship’s infirmary (or “sick-bay”) would’ve been belowdecks—and passengers no doubt would’ve sheltered below during a storm—sources touting the aforementioned theories lack examples of the phrase under the weather in those contexts.
Moreover, many 19th-century instances of being under the weather have nothing to do with poor physical health. It was variously used in reference to personal financial troubles, a political party’s impotence, or an entire city’s failure to prosper.
“Everything is very low-priced here now, except real estate, which holds its own—a fact illustrative of the confidence which has always been felt by our citizens, that Boston could not long remain ‘under the weather,’” a Boston correspondent for New Orleans’s Times-Picayune wrote in 1843.
One article from 1826 even used the expression to mean “drunk.” And while it’s been suggested that the phrase first referred to illness and later expanded to encompass other difficulties, most early references involve those other difficulties. An 1824 update from Key West (called Thompson’s Island at the time) indicated that “piracy is completely under the weather” in the area. Two years later, an announcement about new leadership at the College of William & Mary acknowledged that although the “venerable institution has been long under the weather … we trust that a more auspicious era has commenced.”
In a way, being under the weather was basically the 19th-century version of being in your flop era.
A Different Kind of Weather
As for the phrase’s provenance, clues may be found in how sailors used the words in a literal sense. If a vessel had to make an unscheduled pit stop due to inclement weather, it was often said to have docked “under stress of weather.” Under the weather involves being in some kind of distress as well, so perhaps there’s a link between the two expressions.
It’s also worth pointing out that weather in nautical circles doesn’t always refer to what’s happening in the sky. The weather side of a ship or island is the one that faces the wind: the windward side. Throughout the 19th century, the words under the weather were frequently followed by a term related to the weather side—including under the weather bow, under the weather quarter, and under the weather shore—as opposed to the weather in the sky.
The going gets rougher on the weather side than it does on its counterpart: the lee or leeward side, which is sheltered from the wind. In fact, the word lee meant shelter for centuries before it gained its nautical connotation; and the phrase under the lee had also long been used to describe anything protected or sheltered, at sea or otherwise. So it seems possible that the weather side—with all its implications of struggle and difficulty—inspired under the weather, and its already established antonym of sorts, under the lee, helped it stick.
These, too, are technically just theories—the lexical trajectory of under the weather is about as cloudy as the sky on a stormy day. But it seems safe to assume that it’s related to the notion that sailors dealing with weather in some form or another were often not doing very well.