NOAA works good enough. If you are looking for perfection, good luck searching for it.

I take forecasts for the Sierra with a liberal gain of salt. I have seen forecasts blow up too many times.

I take clothing for the lowest temperature I expect to see, both day hike and backpack plus rain gear. I have never had a surprise...including single digits twice on summit of Mt. Whitney in the summer.

What most do not plan for, which plan for all the time is wind. I have worn my shell pants to the summit two or three times during the summer.