Agua Tibia Wilderness
Sunrise over the Agua Tibia Wilderness
Map showing the location of Agua Tibia Wilderness
Map showing the location of Agua Tibia Wilderness
Map of the United States
Map showing the location of Agua Tibia Wilderness
Map showing the location of Agua Tibia Wilderness
Agua Tibia Wilderness (the United States)
LocationSan Diego and Riverside counties, California, United States
Nearest cityTemecula, California
Coordinates33°25′15″N 116°59′09″W / 33.4208650°N 116.9858598°W / 33.4208650; -116.9858598[1]
Area17,961 acres (72.69 km2) [2]
EstablishedJanuary 5, 1975 (1975-January-05)
Governing bodyU.S. Forest Service, USDA
Bureau of Land Management

Agua Tibia Wilderness (ATW) is a 17,961-acre (72.69 km2) protected area in Riverside and San Diego counties, in the U.S. state of California. It is mostly within the Palomar Ranger District of the Cleveland National Forest.[3] The area was originally protected as the Agua Tibia Primitive Area until January 1975 when it was added to the National Wilderness Preservation System with the passage of Public Law 93-632 by the United States Congress.[2] Between its inception and 1984, the ATW was San Diego County's only officially designated wilderness area.[4] The Spanish name, Agua Tibia, translates as warm water.

Its approximate boundaries are:[5]


There are no permanent streams in the ATW. The highest landform is Agua Tibia Mountain with an elevation of 4,779 feet (1,457 m).[6]

Though the summer climate is hot, with limited shade and no water sources, there were no fires in the ATW for 110 years. In the last two decades, there have been four fires including the Palomar Mountain Fire (1987), the Vail Fire (1989), the Agua Tibia Fire (2000), and the Poomacha Fire (2007).[5] Its pollution exposure is monitored within the San Diego Air Basin.[7]


The Agua Tibia Wilderness is home to rare and endemic plants. These include:

Agua Tibia Research Natural Area

The Agua Tibia Research Natural Area (ATRNA), located within the wilderness, comprises 480 acres (190 ha) of bigcone Douglas-fir—canyon live oak forest. The area was set aside for the study of this forest type in the Peninsular Range province and with emphasis on forest succession, long-range ecological changes and the effects of resource management practices. Bigcone Douglas-fir (Pseudotsuga macrocarpa) is a relict species and is endemic to Southern California. This population on the ATRNA is unique for its relatively great age, size, genetic purity, placement near the southern extent of the species' range, and for its remoteness and lack of disturbance by man. Other notable plants in the research area are Laguna linanthus (Linanthus orcuttii ssp. pacificus) and Hall's monardella (Monardella macrantha ssp. hallii). Both are listed as 1B by the California Native Plant Society's Rare Plant Program.[8][9]


According to a U.S. government geologist writing in 1915, "Near the southern base of Agua Tibia Mountain and 25 miles in a direct line north of west from Warner Hot Springs, warm water (agua tibia), issues along a fault zone that is parallel to the one in Warner Valley. The water rises with a temperature of 92 °F (33 °C) in a marshy area that covers perhaps an acre. It is conducted from a board-curbed pool to tubs in a near-by house, for bathing and laundry use. Bubbles continually rise in the pool and the water is distinctly sulphureted...This water is essentially primary saline in character, being a soft water of moderate mineralization."[10]


  1. ^ "Agua Tibia Wilderness". Geographic Names Information System. United States Geological Survey, United States Department of the Interior.
  2. ^ a b "Agua Tibia wilderness". Retrieved 2008-12-14.
  3. ^ "Dripping Springs Campground, Cleveland National Forest". Archived from the original on 2007-09-21. Retrieved 2007-11-02.
  4. ^ Jerry Schad (September 1998). Afoot & Afield in San Diego County (3rd ed.). Wilderness Press. ISBN 978-0-89997-229-9.
  5. ^ a b "Agua Tibia Mountain – General Information". Tom Chester. Archived from the original on 24 October 2007. Retrieved 2007-11-02.
  6. ^ "Agua Tibia Mountain". Retrieved 2010-08-14.
  7. ^ Bruce D. Ryan (May 1990). "Lichens and air quality in the Agua Tibia Wilderness, California: a baseline study" (PDF). Retrieved 2007-11-02.
  8. ^ "The CNPS Ranking System". Rare Plant Program. California Native Plant Society. Archived from the original on 19 September 2010. Retrieved 2010-08-14.
  9. ^ "Establishment Record of the AguaTibia Natural Research Area" (PDF). US Forest Service. pp. 1–2. Retrieved 2010-08-14.
  10. ^ Waring, Gerald Ashley (January 1915). Springs of California. U.S. Department of the Interior, Geological Survey Water-Supply Papers. U.S. Government Printing Office. p. 47. Water Supply Paper No. 338–339. Retrieved 2023-11-11 – via HathiTrust.