Why do temperatures on mercury vary so much?

Temperatures on Mercury vary dramatically due to its lack of a significant atmosphere, which means there is minimal insulation to retain heat. During the day, the surface can reach temperatures of up to 800 degrees Fahrenheit (427 degrees Celsius) as it basks in direct sunlight. Conversely, at night, temperatures can plummet to about -330 degrees Fahrenheit (-201 degrees Celsius) since there is no atmosphere to trap the heat. This extreme temperature fluctuation is a result of its slow rotation and proximity to the Sun.