Why do joints hurt when the weather changes?

Pressure changes: Inflamed joints are more sensitive to subtle changes in atmospheric pressure. Changing weather is associated with such changes. Almost any underlying joint inflammation/arthritis can act this way.

Barometer sign: There was a rheumatologist in philadelphia who would have his patients go into a chamber where he could change the temperature, humidity and barometric pressure. When he increased the humidity and dropped the barometric pressure, conditions before a thunderstorm people with a variety of muculoskeletal conditions woud have symptoms like you.The implication is this causes microedema.