The planet in our solar system known for its extreme temperatures is Venus. It has a thick atmosphere composed mainly of carbon dioxide, with clouds of sulfuric acid that create a strong greenhouse effect, raising surface temperatures to around 900 degrees Fahrenheit (475 degrees Celsius). This makes Venus hotter than Mercury, despite being farther from the Sun. Additionally, its surface pressure is about 92 times greater than Earth's, similar to being deep underwater. The extreme conditions on Venus make it an inhospitable environment for life as we know it, highlighting the stark differences between planets in our solar system.