Fall at higher altitudes above treeline – bring some good clothing layers to block the wind and cold. And keep your sun hat nice and tight so the wind doesn’t steal it. Whatever shelter you choose, practice putting it up in windy conditions near home to work out your technique, including placing rocks on the corners temporarily while inserting poles, stakes, etc.
+1 on the “rock loops” for tents/tarps – especially crucial if you can’t find a camp spot with some shelter from the predominant wind direction. Above treeline, definitely use big rocks or multiple rocks stacked on each stake, or rocks tied off with “rock loops” without stakes. I like to error on the side of using more rocks and heavier rocks, and I look for camp sites with lots of them. It’s worth the extra 10 minutes it takes to pile extra rocks up, as a buddy of mine learned the hard way…
A few years ago two friends and I were camping in the upper Enchantments in WA above treeline with minimal shelter from the wind. One of my buddies used rocks that were a little too small to stake out his cozy free-standing tent. We returned to camp after a chilly and windy day hike to find his scratched up tent and all his gear strewn for hundreds of feet downwind, including his down bag floating in a small pond. Took a good hour for all three of us to collect nearly all his gear. Luckily he was able to partially dry out much of his gear that afternoon and we were able to lend him enough extra layers to stay safe and reasonably warm overnight. Going solo would mean less margin for such errors.
+1 on sleeping under the stars – a bivy sack is easy to set up and is much less affected by wind. Great option in late summer/Fall when there’s little bug pressure. There are usually fewer bugs above treeline anyway due to wind. A waterproof/breathable bivy works OK in moderate wet conditions, but I’d prefer more shelter in prolonged rain. It’s nice to have a small tarp as well and plan to camp lower if the incoming weather looks really wet.