Union Pass is a mountain pass in Fremont County, Wyoming at about 2,808 m (9,213 ft) above sea level. The nearest town is Jackson, about 71 km (44 mi) away (Union Pass lies E of town). It is listed on the National Register of Historic Places.
Union Pass is a high mountain pass in the Wind River Range in Fremont County of western Wyoming in the United States. The pass is located on the Continental Divide between the Gros Ventre mountains on the west and the Wind River Range on the east. A triple divide exists nearby, where water may flow to the Mississippi River, Columbia River, or Colorado River. The pass was historically used by Native Americans and early mountain men including the Astor Expedition in 1811 on its way west. On the return trip, fearing hostile Indian activity near Union Pass, the Astorians chose a southern route and discovered South Pass. The pass was named by U.S. Army Captain William F. Raynolds in 1860. Raynolds was in charge of the Raynolds Expedition which was exploring the Yellowstone region immediately prior to the Civil War. After mountain man and guide Jim Bridger led the expedition over the...From the Wikipedia article “Union Pass”, licensed under CC BY-SA 4.0.
Sunrise & sunset directions
At Union Pass the sunrise point swings a long way through the year: about 56° (NE) at the June solstice and 122° (ESE) in late December. Sunset moves from 304° (NW) in June to 238° (WSW) in December, and the midday sun climbs to 70° in summer but only 23° in winter.
| Date | Sunrise | Azimuth | Sunset | Azimuth | Noon sun | Daylight |
|---|---|---|---|---|---|---|
| March equinox (Mar 20) | 7:24 AM | 90° E | 7:32 PM | 271° W | 46° | 12h 08m |
| June solstice (Jun 21) | 5:39 AM | 56° NE | 9:05 PM | 304° NW | 70° | 15h 25m |
| September equinox (Sep 22) | 7:07 AM | 89° E | 7:19 PM | 271° W | 47° | 12h 11m |
| December solstice (Dec 21) | 7:50 AM | 122° ESE | 4:47 PM | 238° WSW | 23° | 8h 57m |
Azimuth is measured clockwise from true north (90° = east, 270° = west). Computed for 2026; values change by less than a degree from year to year.
Golden hour & blue hour by month
Mountain passes sit above valleys, so they reward sunrise and sunset with layered ridges, valley fog and long shadows.
| Month (15th) | Blue hour starts | Sunrise | Golden hour ends | Golden hour starts | Sunset | Blue hour ends | Daylight |
|---|---|---|---|---|---|---|---|
| January | 7:18 AM | 7:50 AM | 8:35 AM | 4:24 PM | 5:09 PM | 5:41 PM | 9h 19m |
| February | 6:49 AM | 7:19 AM | 7:59 AM | 5:10 PM | 5:50 PM | 6:20 PM | 10h 32m |
| March | 7:04 AM | 7:33 AM | 8:10 AM | 6:48 PM | 7:26 PM | 7:55 PM | 11h 53m |
| April | 6:08 AM | 6:38 AM | 7:16 AM | 7:24 PM | 8:03 PM | 8:32 PM | 13h 25m |
| May | 5:23 AM | 5:56 AM | 6:37 AM | 7:56 PM | 8:38 PM | 9:11 PM | 14h 42m |
| June | 5:03 AM | 5:39 AM | 6:23 AM | 8:19 PM | 9:03 PM | 9:39 PM | 15h 24m |
| July | 5:18 AM | 5:53 AM | 6:36 AM | 8:17 PM | 8:59 PM | 9:34 PM | 15h 06m |
| August | 5:54 AM | 6:25 AM | 7:05 AM | 7:45 PM | 8:25 PM | 8:55 PM | 13h 59m |
| September | 6:31 AM | 7:00 AM | 7:37 AM | 6:54 PM | 7:32 PM | 8:00 PM | 12h 32m |
| October | 7:05 AM | 7:34 AM | 8:13 AM | 5:59 PM | 6:38 PM | 7:07 PM | 11h 04m |
| November | 6:43 AM | 7:14 AM | 7:57 AM | 4:13 PM | 4:56 PM | 5:27 PM | 9h 42m |
| December | 7:14 AM | 7:46 AM | 8:33 AM | 3:58 PM | 4:45 PM | 5:17 PM | 8h 58m |
Local time (America/Denver), including daylight saving time. Golden hour runs from about −4° to +6° solar altitude, so the morning golden hour begins during blue hour, before sunrise.
Milky Way & night sky
From Union Pass, the Milky Way core is visible in a dark sky from March through September. June gives the longest window (about 3.8 hours on a moonless night), and the core peaks around 18° above the southern horizon. Our light-pollution model puts the sky at about Bortle 1 (excellent dark-sky site), which is excellent for astrophotography.
| Month | Core visible (15th) | Hours | Max altitude | Direction |
|---|---|---|---|---|
| January | Below 10° in darkness | — | -4° | — |
| February | Below 10° in darkness | — | 8° | — |
| March | 5:12 AM – 5:52 AM | 0.7 | 14° | SSE → SSE |
| April | 3:07 AM – 4:47 AM | 1.7 | 17° | SSE → S |
| May | 1:11 AM – 3:51 AM | 2.7 | 18° | SSE → S |
| June | 11:25 PM – 3:15 AM | 3.8 | 18° | SSE → SSW |
| July | 11:12 PM – 1:52 AM | 2.7 | 18° | S → SSW |
| August | 10:15 PM – 11:55 PM | 1.7 | 17° | S → SSW |
| September | 9:10 PM – 9:50 PM | 0.7 | 14° | SSW → SSW |
| October | Below 10° in darkness | — | 8° | — |
| November | Below 10° in darkness | — | -2° | — |
| December | Below 10° in darkness | — | -20° | — |
Window when the galactic core is at least 10° high during astronomical darkness on the 15th of each month. Pick nights within a few days of the new moon. Plan exact nights with the Milky Way planner.
Estimated sky darkness: 1 Bortle 1 — Excellent dark-sky site. The Milky Way casts faint shadows; zodiacal light and airglow are obvious. Modeled zenith brightness ≈ 21.94 mag/arcsec². Aurora needs roughly Kp 6.0+ to show low on the northern horizon here.
Weather & best season
Long-term NASA satellite data for this area show July as the clearest month (about 45% average cloud cover) and May as the cloudiest (73%). July is the warmest month and December the coldest, which matters for gear, snow access and how long batteries last at night.
Average cloud cover (%)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| High °F | 41 | 40 | 57 | 69 | 78 | 85 | 91 | 88 | 83 | 72 | 60 | 43 |
| Low °F | -24 | -31 | -18 | -8 | 7 | 22 | 31 | 29 | 14 | -5 | -24 | -27 |
| Precip. (in) | 1.2 | 1.6 | 1.6 | 2.2 | 3.0 | 1.9 | 1.2 | 1.2 | 1.7 | 1.7 | 1.4 | 1.4 |
Monthly climatology for the surrounding 1° grid cell from NASA POWER (MERRA-2). Mountain sites can be colder and cloudier than the cell average.
Photography tips for this mountain pass
- Summit pull-outs often face one direction; use the sun azimuth table to see whether sunrise or sunset suits the view.
- Wildflowers bloom late at pass elevations — often July to early August in the Rockies and Sierra.
- Check road status before driving: many high passes close seasonally or after storms.
- Look for the road itself as a leading line — switchbacks from above make strong compositions.
- Weather changes fast at elevation; carry layers even in summer.
- Bring a spare battery — cold weather and long exposures drain them fast.
Season: Summer and early autumn are the main season; winter visits depend on plowing and avalanche conditions.
Suggested gear: Telephoto lens, Tripod, Warm layers, Road-condition app. Work out exposures with the depth of field, ND filter and NPF rule calculators.
Nearby photo spots
Other locations within 25 km of Union Pass, closest first.
Mountain Peak
Natural Arch
Waterfall
Mountain PeakWaterfallWaterfallWaterfallCampgrounds nearby (Recreation.gov)
- Green River Lake Lodge18.9 km (11.7 mi) · reservable
- Green River Lakes - Bridger-Teton Nf (Wy)18.9 km (11.8 mi) · reservable
- Whiskey Grove Campground28 km (17 mi) · reservable
FAQ
When is the best time to photograph Union Pass?
What time is golden hour at Union Pass?
Where does the sun rise and set at Union Pass?
Can you see the Milky Way from Union Pass?
Do you need a permit to photograph at Union Pass?
How far is Union Pass from Jackson?
Sources
Location data: Wikidata, USGS GNIS / GeoNames, Wikipedia. Sun, moon and Milky Way times are computed by LWPhoto Atlas for 2026. Climate: NASA POWER. Sky darkness is a population-based estimate (Walker's law), not a measurement. See data sources & licenses.