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 | No moon-free core hours | 0 | 40% |
| February | 12 | February 10 to 16 | 0.9 | 44% |
| March | 31 | March 9 to 15 | 2.1 | 41% |
| April | 54 | April 6 to 12 | 3.3 | 35% |
| May | 67 | May 3 to 9 | 4.5 | 33% |
| June | 66 | June 1 to 7 | 5.8 | 34% |
| July | 54 | July 1 to 7 | 5.5 | 46% |
| August | 47 | August 1 to 7 | 3.6 | 49% |
| September | 30 | September 21 to 27 | 1.9 | 39% |
| October | 12 | October 18 to 24 | 0.7 | 31% |
| November | 0 | No moon-free core hours | 0 | 34% |
| December | 0 | Core not visible | 0 | 41% |
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
- April: April 11 is the best night. The core is above 10 degrees and the moon is down from 1:49 am to 5:09 am, with the moon 31% lit that night.
- May: May 9 is the best night. The core is above 10 degrees and the moon is down from 11:59 pm to 4:29 am, with the moon 19% lit that night.
- June: June 3 is the best night. The core is above 10 degrees and the moon is down from 10:19 pm to 4:09 am, with the moon 1% lit that night.
Clock times are Mountain time with daylight saving applied. The best nights fall around the new moon, so the dates shift by about 11 days each year.
About Guadalupe Mountains National Park
Guadalupe Mountains is a rugged park in West Texas, near the New Mexico line. Guadalupe Peak, at 8,751 feet, is the highest point in the state. The mountains are the remains of an ancient reef from the Permian era, about 260 million years ago, and the walls of El Capitan still look like a ship's prow.
Mescalero Apache lived in these mountains, and later ranchers moved in. The park opened to the public in 1972, partly on land donated by Wallace Pratt, a petroleum geologist. It's far from any city, and remains lightly visited.
Guadalupe Mountains National Park is a national park in Texas. The National Park Service places its center at 31.92 degrees north and 104.89 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 Guadalupe Mountains National Park compares
Its best monthly core score of 67 ranks 19 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 Guadalupe Mountains National Park runs from 31% in October to 49% in August.
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 Guadalupe Mountains National Park, it puts the added glow at about 37% of the natural brightness of a moonless sky (a ratio of 0.371). That makes it 27th 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 Guadalupe Mountains National Park?
April, May and June are the best months. The best week of 2027 is May 3 to 9.
Can you see the Milky Way at Guadalupe Mountains 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 Guadalupe Mountains National Park?
The Park Service models how much artificial light brightens the sky across the lower 48. At the point used for Guadalupe Mountains National Park, it puts the added glow at about 37% of the natural brightness of a moonless sky (a ratio of 0.371). That makes it 27th 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 Guadalupe Mountains National Park?
Yes. A bright moon hides the Milky Way. The best night in May is May 9, when the moon is 19% lit and the core is above 10 degrees from 11:59 pm to 4:29 am.
