Seasonal fragrance is mostly about mood rather than rules. Spring often inspires green, floral, rainy, and fresh scents. Summer tends to bring citrus, fruit, tropical, aquatic, and bright herbal fragrances. Fall is closely associated with apple, pumpkin, woods, smoke, and spice, while winter often leans toward pine, peppermint, baked goods, amber, vanilla, and deeper woods.
You can absolutely ignore the calendar. If you want pumpkin in June or ocean air in December, use it. Seasonal categories are simply a useful way to narrow an enormous number of fragrance choices and match the atmosphere you want to create.
If you enjoy seasonal changes but dislike a complete switch, keep a favorite note and change its companions. Vanilla with airy florals may suit spring, while vanilla with woods or baking spices may feel more autumnal. Citrus can move from a bright summer blend into a winter scent with evergreen notes.
You can also choose by the room rather than the season. A crisp scent may suit your daytime workspace while a warmer one fits your evening routine. Keep unused products stored properly between rotations, and do not feel you need to open a new pack just because the calendar changes.