Reader Jen wrote in to ask, “Why do old injuries ache during crummy weather?”

“Oh, my bones are aching. It must be about to rain.” - Everybody’s grandpa, ever.

The idea that certain aches and pains correspond with, and can even predict, the weather is widespread, and has been around since at least the days of ancient Greece.

The typical explanation for bad-weather-related aches is that the drop in barometric pressure that comes with a storm causes soft tissue and fluid around joints to expand, irritating nerves and causing pain, especially at the sensitized site of an arthritic joint or an old injury.

The scientific evidence for the phenomena, which has been studied since the early 20th century, is mixed.

Some studies have found that changes in barometric pressure increased pain, others found that it decreased it, and still others found no correlation. The influence of temperature and relative humidity has also been studied, and is also unclear. (For more on some of this research, see here and here).

A big hurdle to studying the problem is that the swelling happens on such a small scale that it’s difficult to objectively detect and measure, so researchers have to rely on people’s subjective accounts of pain, which aren’t always reliable and are hard to compare from one person to another.

While one study suggests that the phenomena might be explained by psychological factors like people finding a pattern where there isn’t one, and the influence of the “general plausibility and traditional popularity” idea, most of the research on the subject points out that the frequency of reports makes it hard to ignore, and it deserves further attention and research to find a cohesive explanation.