Never so close to the Sun, at least for this year: at 6.15pm Italians of January 3, 2026 the Earth will reach the perihelionthat is, the point of its orbit at the minimum distance from the Sun. We are talking about a distance of 147,099,894 kmi.e. 4.98 million km less than the maximum distance from the Sun, theaphelionwhich this year will be reached on July 6th.
Despite the maximum proximity to the Sun, we are in the middle of winter, that is, the coldest season. At least here in the northern hemisphere (in the southern hemisphere it is now full summer). The explanation is simple: the variation in the Earth-Sun distance during the year is only 3% about, so if you look closely, not much. The effect therefore exists, but it is completely overshadowed by that due to the real reason why the seasons exist, that is, theinclination of the earth’s axis. This is the factor on which depends how much energy arrives per square meter of surface and therefore what the air temperature will be. We are now close to the winter solstice, so our hemisphere receives solar rays at practically the maximum possible inclination during the year.
When Earth reaches perihelion and why it happens
The Earth’s perihelion in 2026 falls at 6.15pm (Italian time) on January 3rd. From an astronomical point of view, the Earth is not always at the same distance from the Sun because the orbit of our planet (as well as every other orbit) is not perfectly circular but slightly elliptical, that is, “flattened”, as established by Kepler’s first law. This is added to the fact (always established by the first law of the great German astronomer) that the Sun is displaced with respect to the center of the ellipse, in two points which in technical jargon are called fires of the ellipse. This geometric situation accounts for the approximately 5 million km difference between the Earth-Sun distance during aphelion and perihelion.
Because it is winter when the Sun is closest
Let us now explain why it is not the distance from the Sun but the inclination of the Earth’s axis that determines thealternation of the seasons. To understand this, just do some calculations. As we have seen, the difference in distance at the aphelion and perihelion is about 5 million km, that is, less than 3.5% compared to the average Earth-Sun distance (149.6 million km). From the point of view of solar energy received on Earth, this translates into a +6.5% approximately at perihelion relative to aphelion. Not very little in absolute, but in the northern hemisphere the perihelion falls in a period in which the inclination of the sun’s rays it adds up to that of the Earth’s tilt in the Northern Hemisphere (see the right side of the image below).
In fact, remember that the Earth’s axis is inclined by approximately 23.5° relative to the Earth’s orbital plane. Therefore, in the middle of winter in our area the Sun is good at midday 47° lower than the midday Sun in the height of summer. In terms of irradiance, the difference is of –250% approximately, that is, in winter the energy per square meter arriving from the Sun is 2 and a half times lower compared to what we receive in the summer. An effect therefore much more powerful than the +6.5% due to the shorter distance from the Sun.
