A weather API is a set of programming tools that allows developers to access weather data from various sources. This data can include current conditions, forecasts, and historical weather information. By using a weather API, applications can provide users with real-time updates about temperature, humidity, wind speed, and more. These APIs are commonly used in mobile apps, websites, and other software to enhance user experience. For example, a travel app might use a weather API to inform users about the climate at their destination, helping them plan their activities accordingly.