WeatherMate is a tiny portable weather monitor for Windows.
Unlike many similar programs, there's no adware or other hassles. Just unzip the download, run WeatherMate.exe, it detects your location and adds a system tray icon displaying the current temperature. (This uses Fahrenheit by default, but can be changed to Celsius by right-click the icon and selecting "Metric Units".)
Look at the top centre of your screen and you should now see a tiny line. This represents WeatherMate's main window, and if you hover your mouse over the line then it'll appear within a second or two. By default this displays core details like temperature, "feels like", humidity, sunrise and sunset times, but it can also include daily or weekly forecasts, radar images, severe weather alerts and a huge number of US maps ("Current Conditions", "Forecasts", "Severe Weather", "Travel", "Health", "Aviation", "Marine", "Golf", "Farming" - and that's just the categories).
If you don't have time to go browsing all this, no problem: WeatherMate will still warn you of severe weather alerts all on its own, displaying a pop-up in the system tray and even speaking the same message (if speech is enabled in Windows).
All of this is highly configurable, too. You're able to add multiple locations, set the window size and position, and customise the icon, auto-hide behaviour, speech settings and more.
Version 4.9 changes (release notes):
Improved the performance of weather information retrieval.
A versatile weather monitor with a vast choice of US weather maps.