Isa LakeAbout Isa Lake
Isa Lake is a small alpine lake in Yellowstone National Park, Wyoming, notable for sitting on the Continental Divide. It is widely known for having outlets that flow toward both the Atlantic and Pacific drainage basins.
The main attraction is the lake’s unusual hydrology rather than large size; a short roadside pullout and footpath provide easy viewing from the Grand Loop Road. The site is commonly visited en route between the Old Faithful area and the West Thumb/Grant Village area of the park.
The lake was named and mapped during early park surveys and has appeared on visitor maps since Yellowstone’s establishment as a national park. Its status as a curiosity on the Continental Divide has made it a traditional stop for park visitors.
Isa Lake lies inside Yellowstone National Park on the Continental Divide, along the Grand Loop Road in the park’s southwestern section of Wyoming. The site is reachable from the main park road system and is a brief stop on routes connecting major attraction areas.
- Bifurcated drainage: The lake sits directly on the Continental Divide and is one of the few in North America that drains to two different ocean basins.
Nearby Attractions to Isa Lake
Best Time to Visit Isa Lake
Summer offers the easiest access and best road conditions; spring and autumn provide quieter visits if roads are open.
Weather & Climate near Isa Lake
Isa Lake's climate is classified as Subarctic - Subarctic climate with cool summers (peaking in July) and freezing winters (coldest in January). Temperatures range from -16°C to 21°C. Moderate rainfall (702 mm/year).
| Month | Comfort | Temp | Feels | Rain | Sky | Humidity | Wind | UV | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | - | -16° - -3° | -16° | 84 mm | - | - | 3.7 m/s | - | - |
| February | - | -16° - -1° | -14° | 63 mm | - | - | 3.3 m/s | - | - |
| March | - | -14° - 2° | -11° | 61 mm | - | - | 3.6 m/s | - | - |
| April | - | -10° - 5° | -7° | 46 mm | - | - | 3.5 m/s | - | - |
| May | - | -4° - 10° | -1° | 60 mm | - | - | 3.7 m/s | - | - |
| June | - | -1° - 15° | 5° | 61 mm | - | - | 3.7 m/s | - | - |
| July | - | 2° - 21° | 12° | 42 mm | - | - | 3.3 m/s | - | - |
| August | - | 2° - 21° | 11° | 44 mm | - | - | 3.3 m/s | - | - |
| September | - | -2° - 16° | 5° | 50 mm | - | - | 3.4 m/s | - | - |
| October | - | -5° - 10° | -1° | 43 mm | - | - | 3.6 m/s | - | - |
| November | - | -11° - 1° | -10° | 68 mm | - | - | 3.8 m/s | - | - |
| December | - | -16° - -3° | -15° | 80 mm | - | - | 3.5 m/s | - | - |
How to Get to Isa Lake
Isa Lake is accessible directly from Yellowstone’s Grand Loop Road between Old Faithful and West Thumb. From Old Faithful it is a short drive (roughly 15-25 minutes). The pullout and small parking area are immediately adjacent to the road.
Tips for Visiting Isa Lake
- Visit around sunrise to see the lake at its quietest and to catch the low light that makes the twin drainage story visible.
- Park at the designated pullout off the Grand Loop Road - there are interpretive signs explaining how Isa Lake drains to both oceans.
- Combine a stop here with nearby attractions (Old Faithful and West Thumb) for an efficient half‑day route through southern Yellowstone.