Why are weather forecasts often wrong?
Weather forecasts have improved in accuracy over time. This is because of faster computer models and more sources of weather data to run the models. The forecast for 5 days from now is better than the 3-day forecasts that were made twenty years ago. However, there are still times when the weather is rapidly changing or when small weather events like thunderstorms can have large effects on the evolving weather. This makes predicting the weather more than 3 days ahead very difficult. Sometimes a small change in weather conditions from what was expected, like the amount of clouds, can make a very large difference in the daily high or low temperature. Rainfall can also be very spotty in nature, particularly in summertime thunderstorms, and can affect local areas very differently than the forecast for the entire region indicates.
