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Best time to see the Milky Way in Mount Rainier National Park
June, July and August are the best months to see the Milky Way core at Mount Rainier National Park. The odds stay modest even then: from 46.9 degrees north the core only climbs to 14 degrees above the southern horizon, and the park averages 58% cloud. The best week of 2027 is July 1 to 7, when the core is above 10 degrees in full darkness with the moon below the horizon for about 2.1 hours a night.
Jun, Jul and Aug
Best months for the core
14°
Highest point of the core, due south
58%
Average cloud amount over the year
37
Top core score out of 100, in July
The core clears 10 degrees during full darkness on most nights from March to August. In January, February, September, October, November and December it is 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 | 75% |
| February | 0 | Core not visible | 0 | 68% |
| March | 1 | March 11 to 17 | 0.1 | 70% |
| April | 8 | April 7 to 13 | 0.9 | 65% |
| May | 15 | May 4 to 10 | 1.6 | 61% |
| June | 29 | June 1 to 7 | 2.4 | 51% |
| July | 37 | July 1 to 7 | 2.1 | 29% |
| August | 19 | August 1 to 7 | 1.1 | 32% |
| September | 4 | September 1 to 7 | 0.3 | 41% |
| October | 0 | Core not visible | 0 | 58% |
| November | 0 | Core not visible | 0 | 71% |
| December | 0 | Core not visible | 0 | 74% |
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 12:06 am to 2:26 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 11:56 pm to 1:56 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 10:56 pm to 11:56 pm, 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 the park
Mount Rainier National Park is a national park in Washington. The National Park Service places its center at 46.86 degrees north and 121.70 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.
How Mount Rainier National Park compares
Its best monthly core score of 37 ranks 46 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 Mount Rainier National Park runs from 29% in July to 75% in January.
The score ranks months and parks. It is not a forecast for any night, and it leaves out local weather, smoke and light from nearby towns. How the core score works.
Nearest parks
Sources and method
- Sun, Moon and galactic centre positions calculated for the park's latitude and longitude from the low-precision formulas in Paul Schlyter's "Computing planetary positions", with the standard sidereal-time and horizon formulas. The code is checked against known events: new and full moons within 5 minutes, and the September equinox within 1 minute.
- Cloud: monthly mean cloud amount, 25-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2025), from NASA POWER (version v2.10.1, source SYN1DEG), accessed October 19, 2026. Data obtained from NASA Langley Research Center POWER Project.
- Park facts: National Park Service.