This is the best site I have found for weather forecasting. It covers the continental US, and perhaps more, I could not figure that out.
www.wunderground.com
It has proven, through months of experience, to be more accurate than any other site I have found for Portland, Oregon, where I live. It is not totally acurate for the hour by hour stuff. Trust your gut and watch the sky. The forecasts on TV and the newspapers are pitiful by comparison.