Winter Solstice: What You Need to Know
On Sunday, December 21th, the Northern Hemisphere welcome the winter solstice, which brings us the winter and signals the bone-achingly cold days ahead. But many of us still do not understand why the coldest days of the year are usually recorded a month after the winter solstice, even though the winter season supposedly starts on December 21th. Science Times seems to have the answers we need.
For the northern hemisphere, December 21th marks the longest night and the shortest day of the year. However it is quite the opposite for the Southern Hemisphere, known as the "summer solstice," where it is actually the longest day and the shortest night of the year.
Habitants of the Northern Hemisphere, except the parts that are already hit by snow storms and colder than season average weather, will still be able to enjoy not-so-cold weather for about a month or so. So why exactly is the short day of the year so distant from the coldest temperatures?
The gap between the winter solstice and the coldest days of the year, or the summer solstice and the hottest days of the year, is called seasonal lag. The reason behind it is the accumulation of the sun's energy in earth's land and oceans. During the spring, hot summer days, and even warm autumn days, the ground and the oceans absorb energy from the sun, which they release slowly over time. At the time of the winter solstice, this energy has not fully dissipated, keeping the temperature relatively warm.
Summertime also has a similar lag. In the Northern Hemisphere, the hottest day of the year is recorded approximately one month after the summer solstice, which arrives on June 21th. The seasonal lag phenomenon is also the reason why early autumn feels warmer than early spring. The same pattern at play on land and in the oceans during the winter solstice also occurs during the summer solstice. In this case however, it is the absorption, not the release of the sun's energy that results in higher summer temperatures well after the summer solstice.
