Starts around September 22 or 23 . Like the spring equinox, the sun crosses the equator again, signaling the transition into cooler months.
While the astronomical definition of the seasons is based on the Earth's position in its orbit, the meteorological definition is based on the annual temperature cycle. The meteorological seasons are defined as: when do the four seasons start and end
Winter is the coldest and darkest season of the year. In the Northern Hemisphere: Starts around September 22 or 23