It’s not your imagination. The changing weather of the changing seasons can and does affect your hearing.
When the weather alters significantly it’s usually accompanied by swings in barometric pressure, which is the force of the atmosphere around you that is sometimes referred to as the “weight of the air.” Since your hearing is a mechanism that has evolved to interpret sound waves that travel through the air around you and then into your ear, it’s not surprising that changes in barometric pressure will change things inside your ear.
Parts of the inner ear are filled with fluid. Changes in the pressure around that fluid causes changes within that fluid, which causes things like “popping” and a sense of your ears being “full.” It’s the same phenomenon that happens when a plane is ascending or descending, only it’s a natural occurrence.
Another issue is that weather changes at seasonal transitions often mean it’s allergy time as well. Plants release pollen and other substances into the air that your body interprets as threats. This usually causes the release of fluids. Since your ears depend on internal fluids to function, a buildup of fluid in the ears can throw off the ideal balance that normal hearing is based on.
Any medications that cut down on these allergic reactions will help keep your ears in better balance.
If you have a hearing aid, seasonal change can also require an alteration of your routine. In the spring bee pollen can cause obstructions in the microphone of your unit. Cleaning it may become a little more important while the air is full of more particulate matter.
Likewise, increased moisture due to greater humidity or more sweating can also be an issue. If the change of season means things are getting wetter, then taking care to keep your hearing dry is important.