Lassen Park Highway
Thirty miles of CA-89 climbing to 8,512 feet past Sulphur Works, Emerald Lake and the foot of Lassen Peak. Crews start plowing in March or April and spend about two months on it, digging through drifts that reach 40 feet. The park measures the snow at Lake Helen every April 1, and that number tells you most of what you need to know: the road has opened as early as April 28, 1990 and as late as July 26, 2017.
This year
Live plow-season reports load here. For today's conditions, go straight to Lassen Volcanic NP's status page.
Conditions change by the hour at 8,512 feet — check Lassen Volcanic NP's status page before you drive.
Plow progress: Lassen Volcanic NP's plowing updates.
The record
Anywhere from early May to early July. The park sets no opening date and says so plainly — the snow decides. Closes with the first storm that sticks, usually in November. The winter closure covers the 30-mile park highway between the Manzanita Lake entrance in the north and the Kohm Yah-mah-nee Visitor Center in the south.
Will it be open for your trip?
| If your dates start… | The road was already open in | That's |
|---|---|---|
| May 15 | 5 of 47 years | 11% |
| June 1 | 23 of 47 years | 49% |
| June 15 | 34 of 47 years | 72% |
| July 1 | 40 of 47 years | 85% |
| July 15 | 44 of 47 years | 94% |
| August 1 | 47 of 47 years | 100% |
Odds come from the full record below — past springs, not a promise about this one.
Every year on record
| Year | Opened | Closed | Notes |
|---|---|---|---|
| 2026 | May 22 | — | April 1 snow at Lake Helen measured 7.6 feet, matching the thinnest in the record. |
| 2025 | June 27 | October 24 | |
| 2024 | June 20 | December 6 | |
| 2023 | July 1 | December 5 | Plowing did not start until May 15, the latest start in the record. |
| 2022 | June 3 | November 6 | |
| 2021 | May 17 | October 21 | |
| 2020 | May 29 | November 13 | |
| 2019 | June 22 | November 29 | |
| 2018 | May 27 | November 20 | |
| 2017 | July 26 | November 10 | The latest opening in the record, with 20.3 feet still standing at Lake Helen on April 1. |
| 2016 | June 12 | October 30 | |
| 2015 | May 3 | November 8 | The thinnest April snowpack in the record — 7.6 feet at Lake Helen. |
| 2014 | May 19 | December 1 | |
| 2013 | May 24 | December 18 | The latest closing in the record. |
| 2012 | June 1 | November 19 | |
| 2011 | July 16 | November 22 | A 20-foot April snowpack at Lake Helen held the opening into mid-July. |
| 2010 | July 8 | October 23 | |
| 2009 | June 4 | November 18 | |
| 2008 | May 18 | December 12 | |
| 2007 | May 18 | December 6 | |
| 2006 | July 6 | November 11 | |
| 2005 | June 2 | November 8 | |
| 2004 | May 27 | October 28 | |
| 2003 | May 23 | November 7 | |
| 2002 | May 22 | November 13 | |
| 2001 | May 10 | November 15 | |
| 2000 | June 2 | November 17 | |
| 1999 | June 11 | November 19 | |
| 1998 | July 12 | November 10 | |
| 1997 | June 5 | November 14 | |
| 1996 | June 12 | October 18 | The earliest closing in the record. |
| 1995 | July 21 | November 21 | Nearly 24 feet of April snow at Lake Helen pushed the opening into late July. |
| 1994 | May 20 | November 7 | |
| 1993 | June 28 | November 10 | |
| 1992 | May 14 | October 29 | |
| 1991 | May 24 | October 22 | |
| 1990 | April 28 | November 14 | The earliest opening in the record, and the only April opening in it. |
| 1989 | June 6 | October 23 | |
| 1988 | May 20 | November 7 | |
| 1987 | May 15 | November 13 | |
| 1986 | June 7 | November 24 | |
| 1985 | May 18 | October 21 | |
| 1984 | June 4 | October 28 | |
| 1983 | July 2 | November 10 | The deepest April snowpack in the record — 27.6 feet at Lake Helen. |
| 1982 | June 18 | October 25 | |
| 1981 | May 21 | November 3 | |
| 1980 | May 29 | November 21 | The first year in the park's published record. |
Record drawn from NPS: Winter road closures and spring clearing update — road opening and closing dates, 1980 to present · NPS: Alerts & conditions · NPS: Hike and bike the highway during spring clearing . Last checked August 14, 2026.