Weather Underground (or "Wunderground" for short) is a website offering real-time weather information for most cities and towns across the globe. It also offers access to news stories and articles about weather, often by professional meteorologists and other weather experts. If you sign up for an account on the website, you can even log in and offer your input on all things wet, warm, or windy.
Most of the services don't cost any money to use, including viewing the weather or signing up for an account. However, you can get a few other useful services, such as extended-range radar forecasts and local forecasts automatically sent to you via email, if you sign up for a paid subscription at a very low annual rate. Whether you're planning for your next vacation or just want to know what to wear for your errands around town tomorrow, Wunderground is one website that's good to know about.