Space questions, answered
What is the hottest planet in the Solar System?
Venus — not Mercury. Its surface averages about 465°C (870°F), hot enough to melt lead, because a thick carbon-dioxide atmosphere traps heat in a runaway greenhouse effect.
Mercury is closer to the Sun, but it has almost no atmosphere, so its heat escapes and its night side turns bitterly cold. Venus, wrapped in a dense CO₂ blanket, holds its heat day and night — making it consistently the hottest planet, everywhere on its surface.
It's the clearest example in the Solar System of how much an atmosphere matters: Venus and Earth are nearly the same size, but one is a temperate ocean world and the other a furnace.
People also ask
Isn't Mercury the hottest because it's closest to the Sun?
No — Mercury gets hotter in direct Sun, but with no atmosphere it can't hold the heat, so on average Venus is far hotter.
Sources: NASA — Venus