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Yellowstone National Park

Idaho, Montana & Wyoming · Established March 1, 1872

A volcanic plateau that breathes steam and shelters the wild West

Area: 2,219,791 acres
Established: March 1, 1872
Recreation visits: 4,762,988 / yr
States: Idaho, Montana & Wyoming
Highest point: Eagle Peak, 11,358 ft (3,462 m)
Lowest point: Reese Creek, 5,282 ft (1,610 m)

Yellowstone Weather Forecast

Loading the National Weather Service forecast for Yellowstone…

Seven-day outlook at the park's reference point (44.598, -110.547). Elevation changes everything in the mountains — expect colder, windier and wetter conditions on high ground.

Map of Yellowstone National Park

The Park

Yellowstone was the world's first national park, set aside on March 1, 1872, and it remains one of the most extraordinary landscapes on the planet. Beneath its high forested plateau lies one of Earth's largest volcanic systems, and the heat rising from below powers more than 10,000 hydrothermal features, including over 500 geysers. Old Faithful, Grand Prismatic Spring and the travertine terraces of Mammoth are only the most famous.

Yellowstone is equally a refuge for wildlife. Bison have lived here continuously since prehistoric times, gray wolves were restored in 1995, and grizzly bears, elk, moose and pronghorn move across broad valleys like the Lamar and Hayden. The Yellowstone River has carved a golden canyon through altered volcanic rock, and Yellowstone Lake spreads across the caldera at 7,733 feet.

Geography

Yellowstone covers about 2.2 million acres, mostly in northwestern Wyoming with slivers in Montana and Idaho. The heart of the park is the Yellowstone Plateau, a high volcanic tableland averaging around 7,900 feet, ringed by mountain ranges including the Absaroka Range on the east, the Gallatin Range to the northwest, and the Red Mountains to the south.

The Continental Divide winds across the park, sending water to both the Atlantic and Pacific. The Yellowstone River flows north out of Yellowstone Lake, over the Upper and Lower Falls and through the Grand Canyon of the Yellowstone, while the Madison, Firehole and Gibbon rivers drain the western geyser basins and the Snake River heads south.

Most hydrothermal activity clusters in and along the edges of the Yellowstone Caldera, in geyser basins such as the Upper, Midway, Lower and Norris basins, and around West Thumb. Broad, grassy valleys in the north and center of the park, especially the Lamar and Hayden valleys, form the park's great wildlife-viewing corridors.

Landmarks

Old FaithfulAreaThe park's most famous geyser, erupting roughly 17 times a day in the Upper Geyser Basin.
Grand Prismatic SpringAreaA vast, steaming hot spring in Midway Geyser Basin, ringed with orange and gold microbial mats.
Norris Geyser BasinAreaOne of the hottest and most changeable thermal areas in the park.
Steamboat GeyserAreaThe world's tallest active geyser, whose rare major eruptions can reach 300 to 400 feet.
Mammoth Hot Springs TerracesAreaCascading travertine terraces built from calcium carbonate deposited by hot water.
Mud VolcanoAreaAn acidic thermal area of churning mudpots, fumaroles and Dragon's Mouth Spring beside the Yellowstone River.
Grand Canyon of the Yellowstone at Artist PointCanyonA classic overlook of the yellow-walled canyon and the 308-foot Lower Falls.
Yellowstone LakeLake · 7,733 ftA large, cold, high-elevation lake filling part of the Yellowstone Caldera.
Fishing BridgeRiverWhere the Yellowstone River leaves Yellowstone Lake, historically a key spawning area for cutthroat trout.
Hayden ValleyValleyA broad, grassy valley along the Yellowstone River, prime habitat for bison and grizzly bears.
Lamar ValleyValleyThe park's premier wolf- and bison-watching valley in the northeast.
Specimen RidgeAreaA ridge south of the Lamar Valley preserving upright petrified trees buried by Eocene volcanic debris.
Mount WashburnPeakA popular summit with a fire lookout and bighorn sheep, offering views across the caldera.
Obsidian CliffAreaA thick rhyolite flow of volcanic glass quarried by people for thousands of years.
Eagle PeakPeak · 11,358 ftThe highest point in the park, in the remote Absaroka Range along the southeastern boundary.

Geology

Yellowstone's volcanic story is written in three immense eruptions. As the North American Plate has drifted southwest over a stationary source of heat in the mantle, a trail of volcanic centers has marched northeast across the Snake River Plain. Over the last 2.2 million years that activity reached the Yellowstone Plateau, where three cycles of volcanism each climaxed in a caldera-forming eruption.

The first and largest, about 2.08 million years ago, produced the Huckleberry Ridge Tuff, more than 2,450 cubic kilometers of ash and pumice. The second, about 1.3 million years ago, created the Mesa Falls Tuff. The third, about 631,000 years ago, blasted out roughly 1,000 cubic kilometers of material as the Lava Creek Tuff and formed the Yellowstone Caldera that holds much of today's park. Afterward, huge rhyolite lava flows, some among the largest on Earth, repeatedly flooded the caldera, the youngest about 70,000 years ago.

Long before the caldera, a separate episode of volcanism shaped the Absaroka Range. During the Eocene, roughly 53 to 43 million years ago, volcanoes buried forests under ash and mudflows, preserving the upright stumps now exposed on Specimen Ridge. Ice Age glaciers later capped the plateau, scouring valleys and leaving boulders across the Lamar Valley.

Today the heat of the magma system, combined with abundant rain and snowmelt seeping into fractured rock, powers the park's geysers, hot springs, mudpots, fumaroles and travertine terraces. The ground rises and falls as fluids move below, earthquakes are frequent, and violent hydrothermal explosions have blasted out craters over the past 14,000 years.

Deep time

About 53 to 43 million years agoEocene volcanoes of the Absaroka field bury forests that become the petrified trees of Specimen Ridge.
About 2.08 million years agoThe first caldera-forming eruption produces the Huckleberry Ridge Tuff, more than 2,450 cubic kilometers of material.
About 1.3 million years agoThe second, smaller cycle climaxes with the Mesa Falls Tuff eruption.
About 631,000 years agoThe Lava Creek Tuff eruption forms the Yellowstone Caldera.
About 160,000 years agoA smaller eruption creates the West Thumb caldera, now a bay of Yellowstone Lake.
About 70,000 years agoThe most recent rhyolite lava flow erupts on the plateau.
About 13,800 years agoA hydrothermal explosion blasts out the crater now occupied by Mary Bay on Yellowstone Lake.
1959The magnitude 7.5 Hebgen Lake earthquake strikes just west of the park, changing geyser behavior.

The rocks

Huckleberry Ridge TuffEarly Pleistocene, about 2.08 million years
Welded ash-flow tuff from Yellowstone's largest known eruption.
Mesa Falls TuffPleistocene, about 1.3 million years
Deposits of the second caldera cycle, exposed mainly west of the park.
Lava Creek TuffPleistocene, about 631,000 years
The ash-flow sheet from the eruption that formed the Yellowstone Caldera, visible in cliffs near Mammoth and the Gibbon River.
Plateau rhyolite lava flowsPleistocene
Thick, slow-moving lavas that filled the caldera, including the flow exposed at Obsidian Cliff.
Lamar River FormationMiddle Eocene
Volcanic sediments of the Absaroka Volcanic Supergroup that entomb the petrified forests of Specimen Ridge.
Absaroka Volcanic SupergroupEocene
Thick volcanic rocks that build the Absaroka Range, including the park's highest peaks.
Mammoth travertineQuaternary
Calcium carbonate deposited by hot springs, forming the terraces of Mammoth Hot Springs.

Trees, Plants & Ecosystems

1,366vascular plant species recorded

Lodgepole pine forestMuch of the central plateau
The dominant forest across the rhyolite plateau; many stands regenerated after the 1988 fires, when serotinous cones released seeds.
Sagebrush-grassland valleysLamar, Hayden and northern range valleys, including the lowest country near Gardiner
Big sagebrush and bunchgrasses feed bison, elk and pronghorn and support wolves and grizzlies.
Subalpine forest and meadowsUpper mountain slopes
Engelmann spruce, subalpine fir and whitebark pine grow where snow lingers, and whitebark seeds are an important food for bears and nutcrackers.
Alpine tundraSummits of the Absaroka, Gallatin and Washburn ranges
Cushion plants and sticky polemonium hold on above treeline, home to pikas and marmots.
Hydrothermal basinsGeyser basins and thermal areas across the caldera
Heat-loving microbes paint thermal runoff channels, and endemic plants like Ross's bentgrass grow on warm ground.
Lakes, rivers and wetlandsYellowstone Lake and river corridors
Cutthroat trout, trumpeter swans, river otters and moose depend on these cold waters.

Trees

Lodgepole pinePinus contortaThe park's most abundant tree, many of whose cones open after fire.
Whitebark pinePinus albicaulisA high-elevation pine whose fatty seeds feed grizzly bears and Clark's nutcrackers.
Limber pinePinus flexilisGrows on dry, windy ridges and rocky slopes, including near Mammoth.
Engelmann sprucePicea engelmanniiA tall spruce of cool, moist subalpine forests and stream bottoms.
Subalpine firAbies lasiocarpaA narrow, spire-shaped fir of high, snowy forests.
Douglas-firPseudotsuga menziesiiThick-barked trees of lower, drier slopes in the northern range.
Quaking aspenPopulus tremuloidesIts groves on the northern range have been a focus of research into how elk and wolves shape vegetation.
Narrowleaf cottonwoodPopulus angustifoliaA riparian tree of the park's lower river valleys.
Rocky Mountain juniperJuniperus scopulorumFound on warm, dry slopes at the park's lowest elevations near Gardiner.

Wildflowers, shrubs & other plants

Ross's bentgrassAgrostis rossiaeAn endemic grass that grows only on warm, thermally influenced ground in Yellowstone.
Yellowstone sand verbenaAbronia ammophilaAn endemic flower found on sandy beaches along Yellowstone Lake.
Big sagebrushArtemisia tridentataThe silvery shrub of the northern valleys, a vital winter food for pronghorn.
Idaho fescueFestuca idahoensisA key native bunchgrass of the northern range grasslands.
Bluebunch wheatgrassPseudoroegneria spicataA drought-hardy bunchgrass grazed by elk and bison.
Glacier lilyErythronium grandiflorumNodding yellow flowers that bloom at the edge of melting snowbanks.
Arrowleaf balsamrootBalsamorhiza sagittataBig yellow sunflowers that brighten lower slopes in early summer.
Silvery lupineLupinus argenteusBlue-purple flower spikes common in meadows and sagebrush.
Wyoming paintbrushCastilleja linariifoliaWyoming's state flower, with bright red bracts.
Common camasCamassia quamashBlue flowers fill wet meadows in early summer; its bulbs were an important Indigenous food.
Sticky polemoniumPolemonium viscosumA skunky-scented alpine wildflower of rocky summits.
Seep monkeyflowerMimulus guttatusYellow blooms that thrive even along warm thermal runoff channels.
Flowery phloxPhlox multifloraLow white-to-pink mats on open slopes and forest edges.

Wildlife

66mammals
289birds
6reptiles
4amphibians
18fish

Mammals

American bisonBison bisonYellowstone is the only place in the U.S. where bison have lived continuously since prehistoric times.
Gray wolfCanis lupusRestored to the park in 1995, wolves are most often watched in the Lamar Valley.
Grizzly bearUrsus arctosForages on roots, carcasses, cutthroat trout and whitebark pine seeds.
American black bearUrsus americanusMost common in forested areas of the northern park.
ElkCervus elaphusThe most abundant large mammal, with bugling bulls at Mammoth in autumn.
MooseAlces alcesBrowses willows in wet valleys like the Lamar and around Yellowstone Lake.
PronghornAntilocapra americanaSeen on the sagebrush flats near the North Entrance.
Bighorn sheepOvis canadensisOften spotted on cliffs near Mount Washburn and the Yellowstone River.
Mountain goatOreamnos americanusDescendants of animals introduced outside the park, now found in its northern mountains.
Mountain lionPuma concolorA secretive predator of rocky, forested terrain.
Canada lynxLynx canadensisRare and elusive in the park's high, snowy forests.
WolverineGulo guloPresent in very low numbers in remote mountain country.
North American river otterLutra canadensisPlayful hunters of trout along rivers and Yellowstone Lake.
American pikaOchotona princepsGathers flowers and grasses in talus slopes for winter.

Birds

Trumpeter swanCygnus buccinatorNorth America's largest waterfowl, on quiet waters of the Yellowstone and Madison rivers.
Bald eagleHaliaeetus leucocephalusNests near lakes and rivers and hunts fish and waterfowl.
OspreyPandion haliaetusNests on rock pinnacles in the Grand Canyon of the Yellowstone.
Golden eagleAquila chrysaetosSoars over open valleys and mountain slopes.
American white pelicanPelecanus erythrorhynchosNests on islands in Yellowstone Lake and fishes the Yellowstone River.
Sandhill craneGrus canadensisNests in wet meadows and bugles across valleys in spring.
Common loonGavia immerA small breeding population nests on remote lakes in the park.
Harlequin duckHistrionicus histrionicusRides the whitewater near LeHardys Rapids in spring.
Barrow's goldeneyeBucephala islandicaA diving duck of lakes and rivers, nesting in tree cavities.
American dipperCinclus mexicanusDives into fast streams year-round, even in winter.
Great gray owlStrix nebulosaHunts rodents in meadows bordered by forest.
Clark's nutcrackerNucifraga columbianaCaches thousands of whitebark pine seeds, planting future forests.
Mountain bluebirdSialia currucoidesA brilliant blue thrush of open meadows and burned forest.
Common ravenCorvus coraxA clever scavenger that often follows wolves to kills.

Reptiles & amphibians

Prairie rattlesnakeCrotalus viridisThe only venomous reptile in the park, found in the warm, low country near Gardiner.
BullsnakePituophis cateniferA large, harmless snake of dry, open northern valleys.
Rubber boaCharina bottaeA small, secretive constrictor that hides under logs and rocks.
Wandering garter snakeThamnophis elegansThe most commonly seen snake, often near water.
Northern sagebrush lizardSceloporus graciosusThe park's only lizard, sometimes found on warm thermal ground.
Boreal chorus frogPseudacris maculataA tiny frog calling from wetlands soon after snowmelt.
Columbia spotted frogRana luteiventrisBreeds in ponds and slow streams across the park.
Western tiger salamanderAmbystoma mavortiumA large salamander breeding in fishless ponds.

Fish

Yellowstone cutthroat troutOncorhynchus clarkiiA native trout of Yellowstone Lake, an important food for bears, otters and eagles.
Lake troutSalvelinus namaycushA nonnative predator in Yellowstone Lake that the park works to suppress to protect cutthroat trout.
Arctic graylingThymallus arcticusA native, sail-finned fish of cold streams and lakes.
Mountain whitefishProsopium williamsoniA native bottom-feeding fish of the park's rivers.
Redside shinerRichardsonius balteatusA small minnow of lakes and slow streams.

Insects & other invertebrates

Hayden's ringletCoenonympha haydeniiA small brown butterfly of mountain meadows in the northern Rockies.
Milbert's tortoiseshellAglais milbertiA fiery-banded butterfly common near streams and meadows.
Arctic blueAgriades glandonA tiny butterfly of alpine and subalpine meadows.

Species totals are the park's certified NPSpecies checklist (occurrence: present).

Climate & When to Visit

Yellowstone's high elevation gives it a cold, mountain climate with long winters and short summers. Much of the park lies above 7,000 feet, and it can snow in any month of the year. Winter lows frequently drop below 0°F (-18°C), and deep snowpack blankets the plateau from late autumn into spring.

Summer days are pleasant, with highs that can exceed 70°F (21°C), but afternoon thunderstorms can build rapidly and knock temperatures down by 20 degrees or more in minutes. The northern valleys near Gardiner and Mammoth are lower and drier, holding less snow, which is why elk and bison gather there in winter.

Spring
Snow lingers well into May on the plateau; roads open gradually, and bison calves and newly emerged bears make it a prime wildlife season.
Summer
Highs can exceed 70°F, but thunderstorms can drop temperatures sharply; nights are cool and occasional snow is possible even in July.
Autumn
Crisp, clear days and frosty nights, with elk rut bugling in September and October; early snowstorms begin closing roads by November.
Winter
Lows often below 0°F with deep snow; most roads close to cars, and access to interior areas is by snowcoach or snowmobile.

Weather hazards

Hydrothermal areas: Stay on boardwalks and trails, because thin crusts can break over scalding, acidic water.
Wildlife encounters: Stay at least 100 yards from bears and wolves and 25 yards from bison, elk and other animals.
Lightning and sudden storms: Afternoon thunderstorms can bring lightning, hail and a 20-degree temperature drop, so carry rain gear and warm layers.
Cold and hypothermia: Cold water in lakes and rivers and sub-zero winter nights can quickly cause hypothermia.
Winter road closures: Most park roads close to regular vehicles in winter; plan routes and check conditions.

Yellowstone Questions

When is the best time to visit Yellowstone?

Late spring through early autumn offers the most access, with nearly all roads open from about late May through October. September combines smaller crowds, elk bugling and crisp weather, while May and June bring bison calves and active bears. Winter offers a snowy, quiet park reached mainly by snowcoach.

Is Yellowstone a supervolcano?

Yellowstone has produced three enormous caldera-forming eruptions, about 2.08 million, 1.3 million and 631,000 years ago. The most recent lava flow erupted about 70,000 years ago. Scientists at the Yellowstone Volcano Observatory monitor its earthquakes and ground movement continuously.

Where is the best place to see wolves in Yellowstone?

The Lamar Valley in the park's northeast is the most reliable place to watch wolves, especially at dawn and dusk. The Hayden Valley is also good for wolves, grizzlies and bison. Bring binoculars or a spotting scope and keep your distance.

What is the weather like in Yellowstone in summer?

Summer highs can top 70°F, but afternoon thunderstorms often drop temperatures by 20 degrees or more. Nights are cool and snow is possible in any month, so pack a warm jacket and rain gear.

How many geysers are in Yellowstone?

Yellowstone has more than 10,000 hydrothermal features, and more than 500 of them are geysers. That concentration makes the park home to a majority of the world's active geysers.

What are the petrified trees on Specimen Ridge?

During the Eocene, roughly 53 to 43 million years ago, volcanic mudflows and ash from the Absaroka volcanoes buried forests on what is now Specimen Ridge. The trunks were petrified in place, and erosion has exposed many still standing upright.

More parks in the Rocky Mountains

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Sources: www.usgs.gov · www.nps.gov · en.wikipedia.org · en.wikipedia.org · en.wikipedia.org · irmaservices.nps.gov · developer.nps.gov · Official NPS site