WHAT IS WEATHER We experience weather every day We notice if it is raining or sunny and if it is hot or cold outside Weather is the daily state of the atmosphere or air in any given place Weather is different from the climate The climate is what the weather is like in a certain place over a long time The weather is important to people It affects our comfort our food supply and even our safety We base what we will wear each day on 4
the weather It may affect what activities we choose to do too There are many different elements that combine to make each day’s weather These include temperature wind and the moisture in the air A cool sunny day is the perfect weather for a family bike ride On a rainy day people may choose to wear rain jackets and boots and to carry an umbrella The people who study the elements of weather are called meteorologists Why do you think people need meteorologists to tell them about the weather THINK ABOUT IT 5
The Sun affects the weather on Earth in many ways You might know that the energy from the Sun affects the temperature of the air around you However the Sun also causes the winds to blow and the clouds to form This is because the air is heated unevenly The POWERED BY THE SUN These maps show how a cold weather system moved from west to east in North America over the course of four days 6
difference in temperature forces the air to move all the time as warm air rises and cool air sinks The Sun’s energy also heats the water on Earth and it causes it to evaporate The water becomes vapor in the air Water vapor helps form clouds When a liquid is heated to a certain point it evaporates Liquids are made of tiny particles called molecules The heat gives the molecules more energy This causes the molecules to move faster If they gain enough energy the molecules near the surface break away They escape the liquid and enter the air as gas or vapor Water is constantly being recycled in a process known as the water cycle Water evaporates and forms clouds The water then falls back to Earth from the clouds as rain or snow 7
