Theory:

The image below shows a sample weather report. The weather report carries information like the humidity, the temperature during the day as well as night, maximum and the minimum temperature, the rainfall predictions for the day as well as the week, and predicts the likely weather for the day.
 
shutterstock_721500424.svg
 
Humidity
Humidity measures or represents the amount of moisture (water vapour) that is present in the air or atmosphere.
When the amount of water vapour is high, it means the humidity is high, thus sweat released from the body does not evaporate easily, and the person feels uncomfortable and hot.
  
When the amount of water vapour in the air is low, it means the humidity is low, and thus sweat released from the body evaporates easily, and the person feels comfortable and cool.
 
Humidity is expressed as percentage. When the humidity is \(100\%\), it means the air is fully saturated with water vapour.
 
Rainfall
Rainfall is measured through an instrument called the rain gauge. Rain gauge is a measuring cylinder with a funnel to collect the rain water. Rain gauge measures the rain in a particular area in \(millimetre\) (unit).  
Weather
Weather is the daily condition of the atmosphere in terms of pressure, humidity, temperature, sunlight, wind speed, wind direction, and rainfall together etc. at a point of time in a particular place.
 
Elements of weather:
  • Temperature and heat
  • Humidity
  • Wind speed, and its direction
  • Rainfall
  • Cloudiness
The condition of air for a short span is called the weather.
 
Thus, weather is based on all the above elements which sum up together. The individual elements are the factors that decide the weather.
  
Weather is thus not constant and varies from place to place, and varies in different habitats.
  
What causes weather?
  
The changes in the weather is due to the sun, its heat, and the effect of the sun's heat on the air. Sun is a sphere of gases at a very high temperature, and thus the heat that is absorbed or reflected by the surface of the Earth, the ocean, and the atmosphere plays a vital role on the determination of weather in a particular place.
  
That is the reason why the weather varies over a very short period of time. For example it is sunny and bright in the morning, while in the afternoon it becomes cloudy, and the rain starts heavily.
  
The highest temperature that is reached in a day is the maximum temperature, and the lowest temperature that is reached in a day is the minimum temperature. The device called the Maximum-and-Minimum thermometer measures the maximum, and minimum temperatures in a day.
  
The maximum temperature is usually recorded in the afternoon, and the minimum temperature is recorded in the early mornings.  
  
Thus by monitoring the elements of weather, the weather can be predicted in advance and this is called as Weather forecasting. Weather reports are prepared by the Meteorological Department of the Government which collects various data on temperature, wind, and other elements to make the weather prediction.