Winter solstice marks start of a new season

On Monday, if you notice a really short day and a really long night, don't worry. It's just the winter solstice and the beginning of a new season.

The winter solstice, marking the official start of winter, happens at the exact time when the sun is directly positioned over the Tropic of Capricorn. Because the Earth is tilted on its axis by 23.5 degrees, this positioning results in the shortest day and longest night of the year, according to the National Weather Service.

While the night will be long on Monday for residents in the Northern Hemisphere, those living below the equator will experience the opposite effect, with their longest day and shortest night of the year. This is because the North Pole is positioned further away away from the sun at any point during the year, whereas the South Pole is closer to the sun than any point. The only two times during the year when day and night are at almost equal length are during the autumnal and vernal equinox, when the Earth's axis is perpendicular to the sun.

But just because it's the shortest day of the year, it won't necessarily be the coldest. It still takes the Earth some time to lose the energy it absorbed during warmer months, according to National Geographic.

The solstice occurs tonight at 11:48 p.m. ET | 10:48 p.m. CT.