If you plan on climbing in the climbing season, you have to purchase a permit. This article shows you different options obtaining the permit.
Buying permits from the Mount St. Helens Institute
The Mt St Helens Climbing Permits are purchased in advance online at the Mount St. Helens Institute web site.
The permits for the 2016 climbing season are going on sale FEBRUARY 1st, 2016. The non-refundable permit cost is $22.
Buying permits from the permit exchange
If you missed out buying a Mt St Helens Climbing Permit for a certain day, or if you are looking for a last-minute permit, there is a web site, purmit.com, where purchased permits are exchanged. You can check if anyone is selling their permit for a specific day. You can also sell your permit there if you don’t need it after all. The permits on the exchange can only be sold at face value or less.
Climbing in the off-season
You can also climb the mountain in the off-season without having to purchase a Mt St Helens Climbing Permits. You still need to carry a (free) permit on your climb. The amounts of permits per day is not limited in the off-season. The off-season is from November 1st through May 14th. The climbing conditions are of course not always good during off-season. Many people do like to climb the mountain in the winter, but it does require one to be in a really good shape, and special gear is also needed (cramp-ons, ice axe, etc…)