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 | 42% |
| February | 14 | February 10 to 16 | 1.0 | 42% |
| March | 35 | March 9 to 15 | 2.3 | 39% |
| April | 56 | April 6 to 12 | 3.5 | 36% |
| May | 68 | May 3 to 9 | 4.8 | 32% |
| June | 65 | June 1 to 7 | 6.0 | 35% |
| July | 54 | July 1 to 7 | 5.9 | 46% |
| August | 54 | August 1 to 7 | 3.9 | 45% |
| September | 32 | September 21 to 27 | 2.2 | 40% |
| October | 14 | October 18 to 24 | 0.8 | 29% |
| November | 0 | No moon-free core hours | 0 | 31% |
| December | 0 | Core not visible | 0 | 39% |
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 2:32 am to 6:02 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 12:42 am to 5:32 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 11:02 pm to 5:12 am, with the moon 1% lit that night.
Clock times are Central time with daylight saving applied. The best nights fall around the new moon, so the dates shift by about 11 days each year.
About Big Bend National Park
Big Bend sits at the bottom of Texas where the Rio Grande makes a huge U-turn on the Mexican border. In one park you get desert, river canyons and the forested Chisos Mountains, which stay cool when the lowlands are baking. It's also remote, which is why you feel you have it to yourself.
The park was established in 1944, on land the state of Texas had acquired and deeded to the federal government. Before that, the area was home to Indigenous peoples, then Spanish explorers, miners and cattle outfits. Ruins of old ranches and mining camps are still scattered around the park.
The National Park Service says its own measurements show Big Bend has "the darkest night skies of any national park in the lower 48 states," and the park was awarded International Dark Sky Park status in 2012. National Park Service (opens in a new tab).
How Big Bend National Park compares
Its best monthly core score of 68 ranks 18 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 Big Bend National Park runs from 29% in October to 46% in July.
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 Big Bend National Park, it puts the added glow at about 1% of the natural brightness of a moonless sky (a ratio of 0.011). That makes it the 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 Big Bend 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 Big Bend 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 Big Bend National Park?
The Park Service models how much artificial light brightens the sky across the lower 48. At the point used for Big Bend National Park, it puts the added glow at about 1% of the natural brightness of a moonless sky (a ratio of 0.011). That makes it the 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 Big Bend 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 12:42 am to 5:32 am.
