As I already said, you can mostly depend on the weather forecast 3 days out--although not always!

I've had enough issues with unexpected weather that I never want to rely on forecasts, though!

Do take a look at the 7-day list, which is far better. I suspect that the 20*F WM Ultralite is the equivalent of a 15* Marmot bag. Even I can get down to 15*F in mine.

Do note that it most definitely is not yet spring, even officially, much less per actual weather conditions! Not with several inches of snow on the Oregon and Washington beaches the other morning! My grandkids were most displeased because it didn't snow in Seattle (a week of snow days in January wasn't enough!).

I believe the gear lists belong to Packlite, so you might want to take it up with him.