There is no weather on Mercury because Mercury doesn't have much of an atmosphere. There is no wind, rain, snow, storms or clouds. However, during the day, the temperature can soar to 800 degrees Fahrenheit. At night, the temperature can plummet to negative 290 degrees Fahrenheit.
The extremes of temperature seen on Mercury are the result of the lack of atmosphere. What little atmosphere Mercury has is made up of oxygen, sodium, helium, hydrogen and potassium. It is simply too small to have the gravity that would allow it to hold on to a proper atmosphere. Scientists refer to Mercury's atmosphere as its exosphere. It is not stable, largely because of the solar wind.
However, Mercury does have a measurable magnetosphere, which is probably the result of its core. Scientists believe that Mercury's core, like Earth's, is made from molten iron and circulates. Mercury's magnetosphere is strong enough to give it some protection from the solar wind.
Mercury is a bit larger than Earth's moon and, like the moon, is full of craters. Mercury has neither rings nor moons, but it is the fastest planet to orbit the sun. It was named after Mercury, the fleet-footed messenger of the Roman gods.