Breakdown: Why we change seasons each year

Breakdown: Why Summer Occurs

MEMPHIS, Tenn. (WMC) - Out with Spring and in with Summer! The summer solstice occurred today at 12:54 p.m. on June 21, marking the beginning of astronomical summer in the northern hemisphere. Meteorological summer, which includes the three hottest months of the year, started on June 1.

Summer is here
Summer is here (Source: WMC Action News 5 Baron Lynx)

The summer solstice is an annual astronomical phenomenon that brings the longest day of the year in the Northern Hemisphere (and the shortest night). It's also a key cultural event in many ancient and contemporary societies.

Earth's rotational axis is the imaginary line through our planet's center which separates the geographic north and south poles. It's tilted at an angle of about 23.5 degrees, possibly as the result of a collision of another planet-sized object billions of years ago, when the solar system was forming.

As Earth orbits the sun over the course of each year, its axis always points at the same direction in space. That means the Northern Hemisphere is angled toward the sun for half the year and angled away for the other half. The moment when the North Pole is nearest to the sun is called the summer solstice in the Northern Hemisphere. The time of year when the North Pole points farthest from the sun is called the winter solstice.

In the Southern Hemisphere, the solstices are reversed. The winter solstice there comes in late June and the summer solstice in late December. The exact dates of the solstices can vary by a day or two.

When the Northern Hemisphere is tilted toward the sun, sunlight falls at a steeper angle on it to cause the hot months of summer. The farther north you live, the longer the hours of daylight around the time of the summer solstice. Inside the Article Circle, the area within roughly 25 degrees of the North Pole, the sun never sets at this time of year.

Astronomers count the summer solstice as the first day of summer. But though the days are at the longest around the summer solstice, the hottest part of the year is still to come. It takes about a month for the climate of the Northern Hemisphere to warm up in the abundant sunlight — a phenomenon known as seasonal lag.

It’s also getting hotter each summer. According to Climate Central, it shows Memphis is having more days each summer with above average temperatures from 1970 – 2017.

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