Tonight at 11:37 PM MST the Earth will reach its closest point from the Sun in its annual orbit around the Sun. This near point in the Earth's orbit is known as the perihelion. This occurs because the orbit of the Earth is not perfectly circular but slightly elliptical, with the Sun not quite in the center but offset slightly. At the time of perihelion, the Earth will be about 91.4 million miles distant from the Sun. That is about 3.1 million miles closer to the Sun than when the Earth was at its farthest point (aphelion) of about 94.5 million miles early July last year. Around the time of perihelion, the Sun appears to be just a little over 3% larger than it is at the time of aphelion (don’t look to see, you won’t really be able to tell the difference, and it would be very dangerous without adequate protection).
Despite the Sun being closer at this time of year, the northern hemisphere is much cooler than during its early summer aphelion time simply because the tilt of the Earth on its axis causes the Sun’s rays to impact the surface at a much shallower angle, which far overcomes the very tiny warming effect due to being closer to the Sun.
beginning tomorrow, January 4th, the Earth will begin increasing its distance from the Sun once again, reaching its far point in its orbit (aphelion) on July 6th at 1:41 PM MDT.