Planets temp in the Solar System 🤩 Mercury is the closest planet to the Sun, but it is not the hottest. That title is held by Venus. Its dense carbon dioxide atmosphere creates a powerful greenhouse effect, heating the surface to about 460°C. Earth, in turn, is one of the few planets with a temperature suitable for life: an average of 15°C. At the other end of the scale is Neptune, where the temperature can drop to -214°C. This makes it one of the coldest objects in our system. Temperatures on