Weather forecasts help people plan their days and plan for particular meteorogical conditions.
Here in Los Angeles one might not only plan for small temperature changes but also for unusual/inclement situations, such as a rain storm in the middle of summer or unusually warm days in fall. A popular weather site is Weather Underground.
"Weather is always changing because it is affected by many different variables, including temperature, air pressure, cloud formation, wind, humidity and rain. You can tell the weather by simply looking outside. Weather affects what you choose to wear today, or whether you choose to hang your washing outside. But, it can also have severe impacts on the environment and our livelihoods."