page_title: Sonora
section_title: Climate
hierarchical_section_title: Sonora / Geography and environment / Climate
caption_attribution_description: English: Sonoran desert in San Carlos, Sonora, Mexico during the blooming season. Français&#160;: Paysage de l'État mexicain de Sonora, près de Guaymas.
context_page_description: Sonora, officially Estado Libre y Soberano de Sonora, is one of 32 states which comprise the Federal Entities of Mexico. It is divided into 72 municipalities; the capital city is Hermosillo.
  Sonora is bordered by the states of Chihuahua to the east, Baja California to the northwest and Sinaloa to the south. To the north, it shares the U.S.–Mexico border primarily with the state of Arizona with a small length with New Mexico, and on the west has a significant share of the coastline of the Gulf of California.
  Sonora's natural geography is divided into three parts: the Sierra Madre Occidental in the east of the state; plains and rolling hills in the center; and the coast on the Gulf of California. It is primarily arid or semiarid deserts and grasslands, with only the highest elevations having sufficient rainfall to support other types of vegetation.
  Sonora is home to eight indigenous peoples, including the Mayo, the O’odham, the Yaqui, and Seri. It has been economically important for its agriculture, livestock, and mining since the colonial period, and for its status as a border state since the Mexican–American War.
context_section_description: During the Pliocene, the detachment of Baja California, the development of the Gulf of California and the Subartic California current drastically reduced moisture coming into Sonora leading to severe regional aridity in both this state and neighboring Baja California. This created xeric communities and the development of species endemic only to this region.
  There are four major climate regions in the state: dry desert (Köppen BW), arid lands (BS), semi moist lands, and temperate zones (Cwb). Ninety percent of the state has desert or arid conditions. The other two climates are restricted to the areas of the state with the highest altitude such as the Yécora area, the mountains north of Cananea and a strip along the southeast of the state on the Chihuahua border.
  Average high temperatures range from 12.7 °C (54.9 °F) in Yécora to 35 °C (95 °F) in Tesia, municipality of Navojoa. Average low temperatures range from 5.9 °C (42.6 °F) in Yécora to 35.2 in Orégano, municipality of Hermosillo. In the winter, cold air masses from the north reach the state, and can produce below freezing temperatures and high winds at night in the higher elevations, but the temperature can then jump back up to over 20C during the day. Freezing temperatures in the lowlands almost never occur. In February 2011, the Mexican government recorded a low in Yécora of −12C.
  Precipitation is seasonal and most occurs in the higher elevations. In hot and arid or semi arid lands, evaporation vastly exceeds precipitation. Mexico's most arid area, the Altar Desert is located in this state. The east of the state is dominated by the Sierra Madre Occidental, which has less extreme temperatures and relatively more rainfall due to altitude. Most moisture comes in from the Pacific Ocean and the tropics, which is pushed against the Sierra Madre. This cools the air masses, leading to rain and occasionally snow in the higher elevations. While most of the rain falls in the mountainous areas, much of this water finds its way back to the western coastal plains in the form of rivers and streams that empty into the Gulf of California and fill underground aquifers. Most of the year's precipitation falls during the rainy season, which is locally called “las aguas” (the waters). These last from July to mid September, when monsoon winds bring moist air from southerly tropical waters. Most of this is from the Pacific Ocean west of Central America but can also come from Gulf of Mexico as well. This moister flow results in nearly daily afternoon thunderstorms. After the las aguas, there may be additional moisture brought in by hurricanes, which generally move west along the Pacific coast of Mexico and occasionally come inland, especially in southern Sonora. However, these storms tend to drop large quantities of rain in a short time, causing flooding and destruction.
  In the winter, from November to February, there are light rains called equipatas ("horse hoofs", named after the sound the rain makes). These rains come in from the north from the southern extensions of frontal storms that originate in the northern Pacific Ocean. These end by March or April when the fronts are no longer strong enough to reach this far south. They end even earlier in the extreme south of the state as the storm systems retreat, with the dry season lasting eight or nine months in this part of the state. In the north these rains support a wide variety of spring annuals and wildflowers, but the water they supply in the south of the state is still important to help replenish wells.
caption: San Carlos during the wet season
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