Winter in the Northern Hemisphere typically starts on or near December 21, which is around the winter solstice, but the exact date can vary slightly from year to year. If you’re asking about 20 specifically, the most common interpretation is:
- Astronomical winter: begins on the winter solstice (usually December 21 or 22) and ends around March 20 or 21.
- Meteorological winter (for easier year-to-year comparison): always starts December 1 and runs through February.
If you meant a specific year or region, I can tailor the start date to that context.
