Mono winds are strong, dry downslope winds that occur along the western slopes of the central

Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. They are a type of

foehn wind A Foehn, or Föhn (, , , ), is a type of dry, relatively warm downslope wind in the lee of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windw ...

that typically blow from the northeast, descending the Sierra into the foothills. Wind speeds in Mono wind events regularly exceed 50 mph (80 km/h), with gusts recorded over 100 mph (160 km/h). The name "Mono" derives from

Mono Lake Mono Lake ( ) is a Salt lake, saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes Hypersaline lake, high levels of salts to accumulate in the lake ...

and the indigenous

Mono people The Mono ( ) are a Native American people who traditionally live in the central Sierra Nevada, the Eastern Sierra (generally south of Bridgeport), the Mono Basin, and adjacent areas of the Great Basin. They are often grouped under the histo ...

. Mono winds are part of the broader family of California's offshore wind systems, like the

Santa Ana winds The Santa Ana winds, occasionally referred to as the devil winds, are strong, extremely dry katabatic winds that originate inland and affect coastal Southern California and northern Baja California. They originate from cool, dry high-pressure ...

in Southern California and

Diablo wind Diablo wind is a name that has been occasionally used for the hot, dry wind from the northeast that typically occurs in the San Francisco Bay Area of Northern California during the spring and fall. The same wind pattern also affects other parts ...

s in the Bay Area.

Meteorology and causes

Mono winds form when high-pressure systems develop over the

Great Basin The Great Basin () is the largest area of contiguous endorheic watersheds, those with no outlets to the ocean, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja Californi ...

following the passage of cold fronts. The cold, dense air flows westward, pushed by the pressure gradient, and descends the Sierra Nevada, accelerating as it moves downhill and warming

adiabatically Adiabatic (from ''Gr.'' ἀ ''negative'' + διάβασις ''passage; transference'') refers to any process that occurs without heat transfer. This concept is used in many areas of physics and engineering. Notable examples are listed below. A ...

. These conditions occur primarily between October and April. In some cases, strong upper-level winds in the

jet stream Jet streams are fast flowing, narrow thermal wind, air currents in the Earth's Atmosphere of Earth, atmosphere. The main jet streams are located near the altitude of the tropopause and are westerly winds, flowing west to east around the gl ...

enhance these effects, transporting momentum downward and increasing surface wind speeds. This type of Mono wind, often referred to as "Type II," can generate turbulent rotors and mountain waves, making the winds especially destructive and unpredictable.

Geographic distribution

Mono winds are most common in the central Sierra Nevada, especially in and around

Yosemite National Park Yosemite National Park ( ) is a List of national parks of the United States, national park of the United States in California. It is bordered on the southeast by Sierra National Forest and on the northwest by Stanislaus National Forest. The p ...

. They affect communities in Mariposa, Madera, and Tuolumne counties. Topographic features like canyons and passes focus and intensify wind speeds, making some areas more vulnerable than others. While similar downslope winds occur elsewhere in California, the term "Mono winds" specifically refers to those impacting the Sierra region west of Mono Lake. These events are analogous to Santa Ana and Diablo winds, with regional differences in temperature and geography.

Impacts

Forest and property damage

Mono winds have historically caused significant damage to forests, infrastructure, and homes. Their gusty nature often results in widespread treefall, particularly among conifer forests. In January 2021, a severe wind event toppled hundreds of trees in Yosemite, including at least 15 giant sequoias in the Mariposa Grove, damaging park infrastructure and forcing a closure of almost two weeks

Wildfire behavior

Mono winds create dangerous fire weather conditions due to their speed and extremely low humidity. They can rapidly spread existing fires and trigger new ignitions through downed power lines. For instance, the

Mountain View Fire The Mountain View Fire was a fire that erupted near Walker, California, on November 17, 2020. As of December 11, 2020, the fire was fully contained, and claimed one life. The fire crossed the Nevada border into Douglas County. The fire was a g ...

in Mono County destroyed over 90 homes after wind gusts drove the fire through the community of Walker in November 2020.

Aviation hazards

The terrain-induced turbulence from Mono winds can pose serious hazards to aviation. Mountain waves and rotor winds generated during these events are capable of producing severe turbulence and sudden wind shear, particularly dangerous to small aircraft and firefighting operations.

Notable events

* December 12, 1967: A destructive Mono wind event caused widespread damage in Bass Lake and

North Fork, California North Fork (formerly Brown's and Northfork; Mono wa?ahhpY', "cedar grove") is an unincorporated community in Madera County, California, United States. As of the 2020 United States census it had a population of 3,250. For statistical purposes ...

. Estimated gusts over 70 mph toppled trees and downed power lines, resulting in more than $1 million in property damage (in 1967 dollars). * December 7, 1971: Strong Mono winds swept through Yosemite National Park, blowing down over 200 trees. The

Badger Pass Ski Area Badger Pass Ski Area is a small ski area located within Yosemite National Park. Badger Pass is one of only three lift serviced ski areas operating in a US National Park ( Hurricane Ridge Ski and Snowboard Area in Olympic National Park and Bosto ...

suffered major damage when high winds wrecked the chairlift infrastructure. * November 17–18, 2020: The

ignited near Walker, California, during a severe Mono wind event. Gusty conditions rapidly spread the fire, destroying approximately 90 homes and killing one resident. The fire burned over 28,000 acres before containment. * January 19, 2021: One of the most destructive Mono wind events in recent history impacted the central Sierra Nevada. Yosemite National Park was hit especially hard, with hundreds of trees downed, including at least 15

giant sequoia ''Sequoiadendron giganteum'' (also known as the giant sequoia, giant redwood, Sierra redwood or Wellingtonia) is a species of coniferous tree, classified in the family Cupressaceae in the subfamily Sequoioideae. Giant sequoia specimens are the la ...

s in the

Mariposa Grove Mariposa Grove is a sequoia grove located near Wawona, California, United States, in the southernmost part of Yosemite National Park. It is the largest grove of giant sequoias in the park, with several hundred mature specimens. Two of its trees ...

. The park was closed for nearly two weeks due to extensive damage and safety concerns.

References

{{Reflist Föhn effect Mountain meteorology Climate of California Wind Winds