While the Sun may have felt a little closer during this week’s record-setting heat, the opposite is actually true.
As temperatures in Raleigh reached 103 degrees on June 12, shattering the previous record by 5 degrees, Earth was about 94.4 million miles (151.9 million kilometers) from the Sun. Over the next few weeks, our planet will continue moving farther away.
Other WRAL Top Stories
On July 6, Earth will reach aphelion, the most distant point in its orbit, at a distance of 94,502,962 miles (152,087,774 kilometers) from the Sun. By comparison, Earth was about 91.4 million miles (147.1 million kilometers) from the Sun at perihelion on January 3, its closest approach of the year.
The difference between Earth’s closest and farthest distances from the Sun is about 3.1 million miles or roughly 3.3 percent. While this slightly changes the amount of solar energy reaching Earth, the impact on temperatures is negligible. Changes Earth-Sun distance also are not responsible for the seasons.
Instead, the seasons are caused by Earth’s 23.4-degree axial tilt.
During June, the Northern Hemisphere is tilted toward the Sun, allowing sunlight to strike the Northern Hemisphere more directly and remain above the horizon for much longer each day. Around the summer solstice on June 21, Raleigh receives nearly 15 hours of daylight, compared with less than 10 hours around the winter solstice in December.
The higher Sun angle along with longer daylight hours deliver far more energy to the surface than the modest change in Earth-Sun distance.
Will the arrival of the summer solstice bring relief from the heat? Probably not.
Although daylight begins decreasing after June 21, the change is almost imperceptible at first. The days shorten by only a few seconds at a time before the losses gradually grow larger through summer.
The process is similar to a roller coaster cresting its highest hill. The train slows almost to a stop at the top before beginning its descent. Likewise, the length of the day changes very slowly around the solstice before accelerating as summer progresses. The hottest days of the year typically arrive weeks after the solstice, long after Earth has begun moving away from the Sun and daylight has started to decrease.
Also remember that the graph above using National Weather Service temperatures at RDU Airport is visualizing climate data, which is based on years of data. "Will the summer solstice bring relief from the heat?" is a weather question about the coming weeks or days.