The start of winter, also known as the winter solstice, is a significant event that marks the beginning of the cold season in the Northern Hemisphere. The timing of winter's start varies depending on the location and the definition used. In the Northern Hemisphere, winter typically begins on December 21 or December 22, while in the Southern Hemisphere, it starts on June 20 or June 21.
Defining the Start of Winter
There are two main ways to define the start of winter: astronomical and meteorological. The astronomical definition is based on the position of the Earth in its orbit around the Sun, while the meteorological definition is based on the temperature and climate patterns. According to the astronomical definition, winter begins on the day of the winter solstice, which is the shortest day of the year and the moment when the Sun is at its lowest point in the sky.
Astronomical Winter
In the Northern Hemisphere, the winter solstice typically falls on December 21 or December 22, while in the Southern Hemisphere, it occurs on June 20 or June 21. This marks the beginning of astronomical winter, which lasts for approximately 89 days in the Northern Hemisphere and 93 days in the Southern Hemisphere. The winter solstice is also known as the heliacal rising of the Sun, which refers to the moment when the Sun appears to rise above the horizon after a period of being below it.
| Hemisphere | Start of Astronomical Winter | End of Astronomical Winter |
|---|---|---|
| Northern Hemisphere | December 21/22 | March 20/21 |
| Southern Hemisphere | June 20/21 | September 22/23 |
Meteorological Winter
In contrast, meteorological winter is defined as the three-month period with the lowest average temperatures. In the Northern Hemisphere, this typically includes the months of December, January, and February, while in the Southern Hemisphere, it includes the months of June, July, and August. Meteorological winter is often used by climatologists and meteorologists to study and analyze seasonal patterns and trends.
Meteorological Seasons
The meteorological seasons are defined as follows:
- Winter: December, January, and February (Northern Hemisphere), or June, July, and August (Southern Hemisphere)
- Spring: March, April, and May (Northern Hemisphere), or September, October, and November (Southern Hemisphere)
- Summer: June, July, and August (Northern Hemisphere), or December, January, and February (Southern Hemisphere)
- Autumn: September, October, and November (Northern Hemisphere), or March, April, and May (Southern Hemisphere)
What is the difference between astronomical and meteorological winter?
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Astronomical winter is defined as the period between the winter solstice and the spring equinox, while meteorological winter is defined as the three-month period with the lowest average temperatures.
When does winter start in the Northern Hemisphere?
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Winter typically begins on December 21 or December 22 in the Northern Hemisphere.
What is the winter solstice?
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The winter solstice is the shortest day of the year and the moment when the Sun is at its lowest point in the sky.
