I wrote a Python script to download the 1 through 5 day predictions for the weather in the top 50 American cities from the Weather Underground. I’ve got almost 2 years of data now. Here are the RMSE for predictions for all cities. I believe the RMSE for all cities is 2.24, 2.89, 3.68, 4.29, 4.92 degrees F for 1 through 5 days respectively. I put the data up here, but I don’t yet know how to add visualizations. Unfortunately I have forgotten what little statistics I’ve ever learned. I tried a naïve prediction: tomorrow will be the same as today. This scored a RMSE of 6.11, which is significantly worse than even the 5 day forecast. I’ll try some machine learning algorithms on the data. In addition to the temperature, I stored things like weather condition (rain, snow, cloudy, etc) which may help make better predictions. Overall, I guess the weather underground does ok.
