I too have wondered is it due to weather, I live in the tropics and think it is the moist air, the change in pollen content or weather ( sudden downpours cloudy days brilliant sun) as
well as the
various molds and spiders we have. I don't think it is
an allergy as
just a very sensitive nose. Dust gets me, a smell, perfume, the sun but then some days nothing. I noticed this happening when I was pregnant with my first child 17 years ago.