Mercury, the closest planet to the Sun, holds the title of the hottest planet in our solar system. Despite not having the thickest atmosphere, its proximity to the Sun allows its surface to reach scorching temperatures. During the day, temperatures on Mercury can soar up to a blistering 430 degrees Celsius (800 degrees Fahrenheit), hot enough to melt lead.

This extreme heat is due to Mercury's lack of atmosphere to retain heat and the Sun's direct radiation beating down on its surface. The planet's slow rotation also contributes to the temperature difference between its day and night sides, with one side constantly facing the Sun's intense heat while the other side faces the cold darkness of space.