SCIENCE FACTS AHOY:
Actually, not all seasons are 3 months long. Technically, Spring and Summer are longer than 3 months, at over 90 days apiece, while Autumn and Winter are under 90 days in length. Furthermore, Spring and Winter are getting shorter each year, while Summer and Autumn are getting longer.
So no, you can't just divide the 12 months into 4 parts and call it a day.