Meteorologists are scientists that study and predict the weather. They make weather observations on different time scales and compare their observations with various weather prediction models. These models have been created based on weather data gathered over the course of long periods of time. Sometimes, weather can behave in unexpected ways, and cause the prediction to end up being wrong. 

Specialized equipment such as rain radars are used to make short-term weather predictions. Rain radars measure the movement of rainclouds and compare this with observations about wind speed. As a result, the meteorologist can predict when and where it will rain. These predictions are often quite reliable. 

You can find meteorological weather predictions on the internet, in newspapers and on the radio and television. You can also try to predict weather yourself by making observations various weather phenomena. For example, tall and dark clouds often indicate approaching rain fronts.

 Real-time map of clouds over Europe

 Weather predictions and climate diagrams