Why is the winter solstice not the coldest day of the year?

The darkest time of the year is the winter solstice, the days have the least sunlight and the nights are the longest, but the coldest time of the year usually falls about a month after the winter solstice. The cause lies in the Earth’s tilted axis and the way the planet retains heat, according to Live Science.

The Earth’s axis, the imaginary line connecting the North and South poles, is tilted at an angle of 23.4 degrees. This means that one day every year on Earth, the North Pole is the furthest away from the Sun. On other days, the South Pole turns furthest away from the Sun. Those days are the northern and southern winter solstices, respectively, according to Christopher Baird, associate professor of physics at West Texas A&M University. The more the Earth’s surface tilts away from the Sun, the less daylight time it has. The northern winter solstice, the shortest day in the Northern Hemisphere, occurs on December 21, 22 or 22 each year, while the southern winter solstice usually falls on June 20, 21, 22.

The Earth receives most of its warmth from the Sun, so we easily mistakenly think the winter solstice is the coldest day of the year in each hemisphere, according to Baird. However, the coldest temperatures in each hemisphere are usually a month off the solstice, according to Nick Bassill, director of the Center for Weather Hazard Communications at New York University at Albany. In the Northern Hemisphere, that time is mid-January.

In contrast, the summer solstice, the longest day of the year, which occurs on June 20, 21 or 22 in the Northern Hemisphere and December 21, 22 or 23 in the Southern Hemisphere, is usually not the hottest day of the year, according to Jason Steffen , assistant professor of physics and astronomy at the University of Nevada, Las Vegas. For example, the Mojave is hottest in late July, long after the summer solstice, and the Florida Gulf Coast is hottest in August.

The gap between the solstice and the coldest or hottest temperature of the year is because objects such as lakes, oceans, ground, concrete… do not immediately react to colder or hotter temperatures, Bassill explained. . In winter, this means they retain heat from fall and summer longer than the air. The closer a location is to the ocean, the more these seasonal temperature fluctuations are suppressed, as it takes four times more energy to raise the water temperature one degree Celsius than rock. Additionally, because the ocean circulates heat, even when the nights are long, ocean heat currents can keep places warm. For example, many places on the Pacific coast of the United States have warmer winter coldest temperatures than other places at the same latitude because of this effect.