Of course, forecasters don’t just look out the window to prepare the weather report you see on TV. They use a sophisticated weather information network located all over—and above—the globe.
Satellites orbit the Earth constantly. Planes and balloons make daily ascents to gather data. Weather stations in almost every country on Earth contribute data.
As you’ve noticed, forecasters still make mistakes. That’s because a forecast is only a prediction of what’s likely to happen, based on what’s happening now. But nature doesn’t always follow a predictable pattern. So a forecast is only an educated guess, not a guarantee.