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 | 38% |
| February | 12 | February 10 to 16 | 0.8 | 39% |
| March | 35 | March 9 to 15 | 2.1 | 34% |
| April | 60 | April 6 to 12 | 3.3 | 27% |
| May | 78 | May 3 to 9 | 4.4 | 22% |
| June | 79 | June 1 to 7 | 5.7 | 21% |
| July | 44 | July 1 to 7 | 5.4 | 56% |
| August | 47 | August 1 to 7 | 3.6 | 48% |
| September | 33 | September 21 to 27 | 1.9 | 30% |
| October | 13 | October 18 to 24 | 0.7 | 23% |
| November | 0 | No moon-free core hours | 0 | 30% |
| 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 9 is the best night. The core is above 10 degrees and the moon is down from 1:23 am to 4:33 am, with the moon 13% lit that night.
- May: May 9 is the best night. The core is above 10 degrees and the moon is down from 11:23 pm to 3:53 am, with the moon 19% lit that night.
- June: June 4 is the best night. The core is above 10 degrees and the moon is down from 9:43 pm to 3:33 am, with the moon 0% lit that night.
Clock times are Mountain time, which doesn't observe daylight saving. The best nights fall around the new moon, so the dates shift by about 11 days each year.
About Saguaro National Park
Saguaro in southern Arizona is the place to see the giant saguaro cactus, the one with raised arms that appears in every western film. The park has two districts, one on each side of Tucson. A saguaro can live as long as 200 years and doesn't grow its first arm until it's about 50 to 70 years old.
The saguaro forest was made a national monument in 1933 and a national park in 1994. The Tohono O'odham people have long harvested the saguaro fruit.
Saguaro National Park is a national park in Arizona. The National Park Service places its center at 32.21 degrees north and 110.76 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 Saguaro National Park compares
Its best monthly core score of 79 ranks 4 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 Saguaro National Park runs from 21% in June to 56% 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 Saguaro National Park, it puts the added glow at about 12.4 times the natural brightness of a moonless sky (a ratio of 12.415). That makes it 44th 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 Saguaro National Park?
April, May and June are the best months. The best week of 2027 is June 1 to 7.
Can you see the Milky Way at Saguaro 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 Saguaro National Park?
The Park Service models how much artificial light brightens the sky across the lower 48. At the point used for Saguaro National Park, it puts the added glow at about 12.4 times the natural brightness of a moonless sky (a ratio of 12.415). That makes it 44th 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 Saguaro National Park?
Yes. A bright moon hides the Milky Way. The best night in June is June 4, when the moon is 0% lit and the core is above 10 degrees from 9:43 pm to 3:33 am.
