The core clears 10 degrees during full darkness on most nights from February to October. In January, November and December it's out of reach, either too close to the Sun or too low in the dark.
Core score by month
| Month | Core score | Best week | Moon-free core hours a night | Average cloud |
|---|---|---|---|---|
| January | 0 | Core not visible | 0 | 60% |
| February | 1 | February 10 to 16 | 0.1 | 59% |
| March | 12 | March 10 to 16 | 1.2 | 59% |
| April | 25 | April 5 to 11 | 2.1 | 54% |
| May | 43 | May 3 to 9 | 3.1 | 45% |
| June | 73 | June 1 to 7 | 4.3 | 27% |
| July | 86 | July 1 to 7 | 4.1 | 14% |
| August | 55 | August 1 to 7 | 2.6 | 16% |
| September | 21 | September 1 to 7 | 1.1 | 22% |
| October | 4 | October 1 to 7 | 0.2 | 35% |
| November | 0 | Core not visible | 0 | 53% |
| December | 0 | Core not visible | 0 | 62% |
Times are for the best seven nights in each month. Moon-free means the moon is below the horizon. The core counts as visible above 10 degrees in full darkness, when the Sun is more than 18 degrees below the horizon.
The best nights in 2027
- June: June 5 is the best night. The core is above 10 degrees and the moon is down from 11:05 pm to 3:25 am, with the moon 3% lit that night.
- July: July 1 is the best night. The core is above 10 degrees and the moon is down from 10:45 pm to 2:55 am, with the moon 5% lit that night.
- August: August 1 is the best night. The core is above 10 degrees and the moon is down from 10:15 pm to 12:55 am, with the moon 0% lit that night.
Clock times are Pacific time with daylight saving applied. The best nights fall around the new moon, so the dates shift by about 11 days each year.
About Lassen Volcanic National Park
Lassen Volcanic in northern California shows off all four types of volcano in a single park. Lassen Peak, the star, is a plug dome volcano that you can hike. The park also has bubbling mud pots and steaming vents at Bumpass Hell, and quiet lakes among the pines.
Lassen Peak erupted repeatedly from 1914 to 1917, and the eruptions caught national attention. The area was made a national park in 1916. It was the last volcano to erupt in the lower 48 until Mount St. Helens in 1980.
Lassen Volcanic National Park is a national park in California. The National Park Service places its center at 40.49 degrees north and 121.41 degrees west, and the sky calculations on this page use that point. Visitor information, fees and alerts are on the park's own page. National Park Service (opens in a new tab).
How Lassen Volcanic National Park compares
Its best monthly core score of 86 ranks 1 of 54 national park units that can see the core. The highest is Lassen Volcanic National Park at 86, and the lowest is Voyageurs National Park at 13. Cloud at Lassen Volcanic National Park runs from 14% in July to 62% in December.
The score ranks months and parks. It isn't a forecast for any night, and it leaves out local weather, smoke and light from nearby towns. How the core score works.
How dark is the sky?
The Park Service models how much artificial light brightens the sky across the lower 48. At the point used for Lassen Volcanic National Park, it puts the added glow at about 9% of the natural brightness of a moonless sky (a ratio of 0.09). That makes it 13th darkest of the 47 parks it covers. Lower is darker. This is a model, not a reading taken at the park, and it describes one point, so the edges of a large park can differ.
Questions people ask
When is the best time to see the Milky Way at Lassen Volcanic National Park?
June, July and August are the best months. The best week of 2027 is July 1 to 7.
Can you see the Milky Way at Lassen Volcanic National Park all year?
The core clears 10 degrees during full darkness on most nights from February to October. In January, November and December it's out of reach, either too close to the Sun or too low in the dark.
How dark is the sky at Lassen Volcanic National Park?
The Park Service models how much artificial light brightens the sky across the lower 48. At the point used for Lassen Volcanic National Park, it puts the added glow at about 9% of the natural brightness of a moonless sky (a ratio of 0.09). That makes it 13th darkest of the 47 parks it covers. Lower is darker. This is a model, not a reading taken at the park, and it describes one point, so the edges of a large park can differ.
Does the moon matter at Lassen Volcanic National Park?
Yes. A bright moon hides the Milky Way. The best night in July is July 1, when the moon is 5% lit and the core is above 10 degrees from 10:45 pm to 2:55 am.
