The order of planets from hottest to coldest is almost in order of its proximity to the sun, because the sun is the primary heat source. However, another factor that effects a planet's atmospheric temperature is the gases that make up the atmosphere. Gases like carbon dioxide cause a greenhouse effect trapping heat in.
Venus' atmosphere consists of carbon dioxide and nitrogen, with clouds of sulphuric acid droplets.The greenhouse gases in Venus' atmosphere trap heat and make it so hot that you can melt lead. In fact, any of NASA's exploratory spacecraft that has landed on Venus has only been able to last for a few hours. With atmospheric temperatures of 462 degrees Celsius, the second planet is the hottest.
In photos of Mars, you can see the ice in the atmosphere. Due to its tilt, Mars has seasons like Earth. In the winter, it can go as low as -51.7 degrees Celsius. The current temperatures and atmospheric conditions make it impossible for water to last very long on the planet -- making it doubtful that life exists on Mars. However, scientists have found evidence that water once existed on the planet.
On parts of Earth, it can get as cold as -52.2 degrees Celsius, similar to Mars' coldest temperatures.
As the planet closest to the sun, you might expect Mercury to be one of the hottest planets and it is. It is also one of the coldest. Because Mercury doesn't have an atmosphere, the side of the planet that faces the sun can reach temperatures of 426 degrees C, but on the side that faces away from the sun and its lowest temperature can drop to -143 degrees Celsius.
Known for its rings made of ice chunks and rock, Saturn's lowest temperatures can get to -142 degrees Celsius. If you weigh 45.4 Kilogram on Earth, you will weigh approximately 48.5 Kilogram on Saturn. The atmosphere is made primarily of helium and hydrogen
The biggest planet in our solar system contains a system of moons and rings that make it like a minisystem. Jupiter has 50 moons -- four large moons and 46 smaller moons. The massive planet can get as cold as -112 degrees Celsius. Like Saturn and Uranus, the atmosphere is made up of hydrogen and helium.
With a temperature of -181 degrees Celsius, Uranus is the coldest planet in the solar system. The atmosphere is made up of methane, hydrogen and helium -- the methane giving it its green look. Most of the mass of Uranus is made up of water, methane and ammonia ice.
Since Pluto was classified as a dwarf planet in 2006, Neptune became the farthest planet from the sun. It is no surprise that, 30 times farther from the sun than Earth, Neptune is one of the coldest planets. It has a temperature of -101 degrees Celsius. The atmosphere, similar to Uranus, consists of hydrogen, helium and methane. Scientists believe that another unknown gas exists in the atmosphere, because it appears to be a bright blue, as opposed to the Uranus' blue-green that comes from the methane.