In the PNW most people hike July-September and this concentrated use can put considerable strain on the trails. To control the adverse impact, Oregon is now expanding permit areas to limit the number of hikers and the same is likely to happen in Washington state in the years to come. The popular area known as the Enchantments, had over 17,000 visitors in 2017 with 3000 overnight permits issued (over 20,000 people applied). These permits are just for six months—May 15 through October 31. July and August probably get the highest number of visitors.
In the hiking community, everyone is expected to follow voluntary leave-no-trace (LNT) practices. However, if even 1% of 10,000 visitors per season on a 20 mile trail don’t know or don’t care about LNT practices and leave garbage or human excrement along the trail, that’s 100 incidents of the environment being trashed each year.