Tornadoes are usually a result of a very large thunderstorm or, a super cell. During the storm warm air and cold air collide and they twist and form a tunnel. When the tunnel touches the ground that forms a tornado.
Cold fronts form when cold and dense air moves into and area and pushes the warmer air upward.
Droughts can be caused by not receiving rain or snow over a period of time.
Flooding occurs most of the time from heavy rainfall. Flooding can also be caused by a storm surge associated with a tropical cyclone, a tsunami, or a high tide.
A warm front happens when warm air pushes into colder air.
Hail forms when updrafts from thunderstorms are strong enough to carry rain drops above the freezing level. The hail can grow as additional water freezes onto it.
Hurricanes begin as tropical storms over the warm moist bodies of water. The moisture evaporates and it rises until large amounts of heated air are twisted high into the atmosphere. The winds begin to circle counterclockwise north of the equator or clockwise south of the equator. Around the eye of a hurricane the winds can move at speeds between 74 and 200 miles per hour.
Warm air and water droplets rise. When the air holds a lot of water droplets, clouds form. If a lot of water droplets gather in the clouds then the clouds become heavy. gravity causes the water to fall as rain.
Small bits of ice bump into each other and create an electric charge. The positive charges form at the top of the cloud and the negative charges form at the bottom of the cloud. This causes a positive charge in the ground beneath the cloud. The charge concentrates around anything that sticks up from the ground and the charge coming up from these points connects with a charge reaching down from the clouds and the lightning strikes.
Thunder happens when lightning strikes. The electricity that passes through the air when lightning strikes causes air particles to vibrate. The vibration are heard as a sound, Also the lightning is hot and it heats up the air around it. The hot air expands very quickly and pushes the air particles apart creating more vibrations.
Snow is formed when temperatures are low and there is more moisture in the form of tiny ice crystals in the atmosphere. When the tiny ice crystals collide they stick together in clouds to become snowflakes. If enough stick together then they become heavy enough to fall to the ground.