The planet in our Solar System that experiences the hottest temperatures is Venus. Despite Mercury being the closest planet to the Sun, Venus's thick atmosphere, composed mainly of carbon dioxide, creates a runaway greenhouse effect. This causes surface temperatures to reach around 900 degrees Fahrenheit (475 degrees Celsius), making it the hottest planet. The high-pressure atmosphere also contributes to these extreme temperatures, creating conditions that are hellish by human standards. Venus's thick clouds of sulfuric acid further complicate its environment and prevent heat from escaping, ensuring that its surface remains blisteringly hot at all times.