Final answer:
Earth is closest to the Sun, or at perihelion, around January 3-5 each year.
Step-by-step explanation:
Earth reaches perihelion, the point in its orbit where it is closest to the Sun, typically around January 3-5. This event occurs because Earth's orbit is an ellipse rather than a perfect circle. While Earth is in perihelion, it is roughly 147 million km from the Sun. Interestingly, this happens during the winter for the Northern Hemisphere, which illustrates the fact that the Earth's distance from the Sun is not what causes the seasons; instead, the tilt of Earth's axis is the primary reason for seasonal temperature changes.