As an experiment, several trips ago and over the course of perhaps 5 years, I have been tracking the weather forecasts from 2 weeks out until my day of arrival.
My experience is that every day of my trip, the forecasts will cycle through almost every possibility.
In other words, at 14 days out, for a particular day, the weather might say sunny. At 13 days, partly cloudy. At 12 days, mostly cloudy. At 11 days, sunny. At 10 days, rain.
My conclusion is that the long term forecasts are practically useless--except for getting me baselessly worried or happy LOL.
Two to three days out is the most they can be trusted.
I track weather.com, accuweather, and WESH. WESH is pretty good--which is why I assume they don't give long range. I also see accuweather gives a 45 day forecast! Who are they kidding?