Meteorology is not an exact science. No insult intended to meteorologists, it's just that those darn butterflies keep flapping their wings and making hurricanes and whatnot.
And predicting the weather is uncertain at best. Weather predictions for the same time period from two different sources will probably not be exactly alike.
But this is a little extreme:
Hey, Yahoo, hey, Forecastfox — y'all are not helping your reputation for accuracy...