The planet with the widest range of temperatures on its surface is Mercury.

Here's why:

* No atmosphere: Mercury has a very thin atmosphere, which means there's very little to trap heat or moderate temperatures.

* Close to the sun: Being the closest planet to the sun, Mercury receives intense solar radiation. This leads to scorching daytime temperatures.

* Slow rotation: Mercury rotates very slowly, which means one side faces the sun for a very long time, getting extremely hot. The other side, in the dark, experiences extreme cold.

Temperatures on Mercury:

* Daytime: Up to 800°F (427°C)

* Nighttime: -290°F (-180°C)

This gives Mercury a temperature range of over 1,000°F (550°C), the widest of any planet in our solar system.