I feel your pain. When the weather is in the 70's or higher, my sinuses are fine. Once temperatures start getting down to 50°F at night or cooler, my ears begin to plug and it's almost as if a muscous ball accumulates in my head. It just floats around and sometimes give me a sinus infection. Sometimes part of it drains into my stomach and causes horrible amounts of pain in the morning.
No allergy medication, humidifier, air purifier or amount of fluids I drink seem to affect this ball of mucous. It does not prevent me from breathing through my nose unless I lay down. Even then, it only affects my left nostril.
I choke on it all winter long and right around May, when my allergies flare up, everything drains out of my head in a month long "cold" and then I feel great all summer long.
It's really frustrating. Hopefully someone will figure this out eventually. I've been searching around and there are a lot of people with similar problems so it HAS to be something!