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First of all, you’re not alone in feeling pain when the weather turns sour. As Harvard Medical School professor Dr. Robert Jamison wrote in a 1996 paper that reviewed the influence of weather on pain, “Hippocrates was the first to note, in about 400 b.c., that many illnesses were related to changes in season.” Weather-related pain has given us expressions such as “aches and pain, coming rains,” and “feeling under the weather.”

There are plenty of anecdotes of grandmothers who can predict a change in weather with a throbbing hip, and athletes whose old injuries ache when it’s about to rain. In the past 2,400 years, however, researchers a solid, evidence-based explanation as to why this happens.

The most popular theory blames the drop in atmospheric pressure that accompanies rain. “Think of it like blowing up a balloon,” Jamison says. “There’s inside air pushing out, and outside air pushing in.” Atmospheric pressure is always pushing on our bodies in a similar way. If the pressure outside of the body drops, gasses inside the body can expand—particularly the gasses dissolved in the fluid surrounding your joints and tendons.

Now consider your injury. “Think about pain as nerves that have been irritated. Somehow they didn’t heal right, or they might be inflamed,” Jamison says. That expansion of fluid around your damaged Achilles “might be microscopic, but it can really trigger these nerve endings” by putting additional pressure on them, causing pain, Jamison says.

As for the temperature, the theory goes like this: cold may cause muscles to tense up, and that contraction can also aggravate those damaged nerves.

Unfortunately, there’s not a lot you can do about it without taking drugs. Moving to a warmer, drier place like Phoenix, Jamison wrote in his paper, may not do much good. The body gets used to the climate it’s in, so “relative changes in weather trigger an increase in pain regardless of the actual weather.”

The Bottom Line

A drop in atmospheric pressure may trigger an increase in the pressure of your body’s fluids on damaged nerves, causing pain.