33 Hydrothermal features
The hydrothermal features in Lassen Volcanic National Park include roaring steam and volcanic-gas vents, thumping mud pots, boiling pools and steaming ground. Water from rain and snow feeds the hydrothermal system. Deep
underground, the water is heated by molten to form boiling pools and mud pots. Super-heated
steam reaches the surface through fractures as found at Bumpass Hell and Sulphur Works.
The changing seasons of Lassen
Spring: April to June the weather is warming up though the nights can still be below freezing. Higher elevations are still snow-filled. Conditions permitting, the road begins to open and lakes begin to thaw.
Summer: June to mid-September the park is sunny and dry with cool nights. Snow can linger above 8,000 feet until late August. The Main Park Road is usually open. Campgrounds may fill on weekends. Ranger programs are in full swing.
Fall: mid-September to November the park is mild during the day and cool at night with a potential for thunderstorms. Light snows may begin in October. The trails are usually still clear. The Main Park Road is open until November, weather permitting.
Lassen directions The Southwest park entrance is about 45 miles east of Red Bluff on Highway 36. (530) 595-4444
Winter: November to April the park is snowbound and cold. The Main Park Road is only open to the
Southwest area and the Loomis Ranger station.
