Yup, I also got a headlamp. Anyway, how hard is it to follow the trail in the dark? It seems that the first mile or two should be easy to follow, but I've heard stories of people getting lost between Outpost Camp and Trail Camp. My plan is to tag along with another hiking group but am concerned that it won't work if they're going too fast.
Also, how accurate are weather forecasts at this time of the year? Right now (fingers crossed), the forecast calls for clear skies, calm winds, and daytime summit temps in the 50s from Thursday through Sunday. I'll check it again the day before, and if it holds, I'm tempted to just wear a T shirt, pants, and a hoodie and not bring any other clothes to keep weight to a minimum.
The Whitney trail is typically VERY easy to follow. As you say, there are some spots where you might get a little confused on the way up. But nothing too serious. If you are concerned with getting lost, My recommendation is to download a GPS app (like AllTrails or Hiking Project) on your phone and make sure you have a way to keep it charged (get a powerbank with enough capacity).
Weather forecasts are generally quite accurate as you approach your hike date. What I have noticed is that precipitation chance is the wildcard here. If there is no chance of precipitation in the forecast, you are almost always guaranteed a completely dry hike. It’s when the weather is in a somewhat active monsoon pattern and there is a chance of precipitation (especially above, say, 15-20%) that rain or thunderstorms become a concern. So keep a lookout. Of course, September is generally a safer bet as far as thunderstorms than July or August.
As far as clothes, I myself don’t go too crazy. What you list sounds doable. But for a more comfortable hike (and lighter weight), I would make the T shirt a moisture wicking shirt, wear a pair of hiking pants instead of jeans, and carry a lightweight puffer instead of your average hoodie. Also, I tend to prefer a long sleeved t-shirt vs short sleeves. This helps to keep the sun off me, and allows me to apply less yucky sunscreen. But if you are okay with your clothing choice and don’t have/don’t want to get these things, you will likely be fine.
