Sonoita American Viticultural Area

Much of the Sonoita AVA has a Growing Season Temperature¹ between 66°F and 70°F (19°C and 21°C), based on data² from 1981 through 2010. Some far western and far eastern areas are warmer and have long-term normal values between 70°F and 75°F (21°C and 24°C).

Growing Season Temperature is the average temperature between April 1 and October 31. It is a common climate-viticulture classification used to compare winegrape-growing regions and to gauge which varieties might do well in an area. Different varieties require different amounts of heat accumulation during the growing season to ripen fruit.

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¹ Jones GV and colleagues (2005)
² TopoWx ("Topography Weather")

The central part of the Sonoita AVA from north to south has Winkler Index³ values between 1944 and 2222, based on data² from 1981 through 2010. Most of the western and eastern areas have long-term normal values that are greater and between 2222 and 2700.

Winkler Index values are cumulative growing degree days (10°C-based) between April 1 and October 31. It is a common climate-viticulture classification used to compare winegrape-growing regions and to gauge which varieties might do well in an area. Different varieties require different amounts of heat accumulation during the growing season to ripen fruit.

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² TopoWx ("Topography Weather")
³ Winkler AJ and colleagues (1974)

Most western, northern, and eastern areas of the Sonoita AVA have Huglin Index⁴ values between 2700 and 3000, based on data² from 1981 through 2010. The central and southern parts have long-term normal values that are lower and between 2400 and 2700.

Huglin Index values are cumulative growing degree days (10°C-based) between April 1 and September 30 that additionally account for maximum temperature and daylength. It is a common climate-viticulture classification used to compare winegrape-growing regions and to gauge which varieties might do well in an area. Different varieties require different amounts of heat accumulation during the growing season to ripen fruit.

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² TopoWx ("Topography Weather")
⁴ Huglin P (1978) Nouveau mode d’évaluation des possibilités héliothermiques d’un milieu viticole. Comptes Rendus de l’Académie d’Agriculture de France, 64, 1117-1126

Almost all of the Sonoita AVA has values of Biologically Effective Degree Days⁵ between 1600 and 1800, based on data² from 1981 through 2010.

Values of Biologically Effective Degree Days are cumulative growing degree days (10°C-based) between April 1 and October 31 that additionally account for how vine growth rate differs at different temperatures, daylength, and diurnal temperature range. It is a common climate-viticulture classification used to compare winegrape-growing regions and to gauge which varieties might do well in an area. Different varieties require different amounts of heat accumulation during the growing season to ripen fruit.

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² TopoWx ("Topography Weather")
⁵ Gladstones J (1992)

Central and northern parts of the Sonoita AVA have an average date of the last spring freeze during the second half of April, based on data² from 1981 through 2010. Areas immediately west, south, and east have long-term normal dates during the first half of April. Those farther west and east mostly have dates during the second half of March.

The last spring freeze is the latest occurrence of daily minimum temperature below 32°F (0°C) from January 1 through July 31. Freezing temperatures close to the start of the growing season can damage vines and reduce yield.

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² TopoWx ("Topography Weather")

Much of the central part of the Sonoita AVA from north to south has an average date of the first fall freeze during the first half of November, based on data² from 1981 through 2010. Isolated areas in the north-central part have long-term normal dates during the second half of October. Most western and eastern areas have dates during the second half of November.

The first fall freeze is the earliest occurrence of daily minimum temperature below 32°F (0°C) from August 1 through December 31. Freezing temperatures close to the end of the growing season can damage vines and unharvested fruit, as well as curtail post-harvest photosynthesis and carbohydrate accumulation.

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² TopoWx ("Topography Weather")

Limestone is a known parent material in southwestern and northeastern parts of the Sonoita AVA.¹ Igneous rock, quartzite, schist, granite and gneiss, as well as igneous and metamorphic rock also occur in northeastern areas.

Parent material is the type of bedrock from which soil forms. As a component of vineyard soils, it influences water infiltration, storage, and drainage, erodibility, pH, nutrient availability, and heat absorption, which affect root, canopy, and fruit growth.

¹ Gridded Soil Survey Geographic (gSSURGO) Database for Arizona, United States Department of Agriculture, Natural Resources Conservation Service, July 2020 Release. Not all areas have complete or available data.

Conglomerate and sandstone are the most abundant rock types in the northwestern, north-central, central, and southeastern parts of the Sonoita AVA.² Gravel, sand, sandstone, siltstone, rhyolite, and felsic metavolcanic rock occurs in many northeastern and west-central areas.

Major rock types are the most common solid, loose, and unstratified rocks, defined by composition, texture, and origin. As a component of vineyard soils, they influence water infiltration, storage, and drainage, erodibility, pH, nutrient availability, and heat absorption, which affect root, canopy, and fruit growth.

² US Geological Survey Mineral Resources, Arizona geologic map data

Known depths to bedrock are 12 to 24 inches in the western, northeastern, and southeastern parts of the Sonoita AVA.¹ Areas with depths less than 12 inches also occur in the northeastern and southeastern parts.

Depth to bedrock represents the distance from the soil surface to the top of a restrictive layer, such as bedrock and other dense layers. As a component of vineyard soils, such restrictive layers can impede water drainage and restrict root depth.

¹ Gridded Soil Survey Geographic (gSSURGO) Database for Arizona, United States Department of Agriculture, Natural Resources Conservation Service, July 2020 Release. Not all areas have complete or available data.

Loam is known to occur in areas throughout the Sonoita AVA.¹ Sandy loam and silt loam are common along perennial, intermittent, and ephemeral surface water features like Ciénega Creek and Babocomari River. Areas of fine sandy loam exist along the eastern boundary of the AVA, as do areas of sandy clay along the southern boundary.

Texture represents the relative proportions of mineral grains in soil based on their size. As a component of vineyard soils, it influences water infiltration, storage, and drainage, erodibility, pH, nutrient availability, and heat absorption, which affect root, canopy, and fruit growth.

¹ Gridded Soil Survey Geographic (gSSURGO) Database for Arizona, United States Department of Agriculture, Natural Resources Conservation Service, July 2020 Release. Not all areas have complete or available data.

Almost all of the Sonoita AVA has well-drained soils.¹ Areas of somewhat excessively, moderately well, and somewhat poorly drained soils additionally exist in the east-central and southeastern parts.

Drainage class refers to the rate at which water drains from soil, how frequently water occurs in soil, and at which soil layers water is found. As characteristics of vineyard soils, these conditions influence soil moisture and nutrient and oxygen availability, which affect root, canopy, and fruit growth.

¹ Gridded Soil Survey Geographic (gSSURGO) Database for Arizona, United States Department of Agriculture, Natural Resources Conservation Service, July 2020 Release. Not all areas have complete or available data.

Many areas in the Sonoita AVA have available water storage in the top approximately 40 inches of soil greater than three inches.¹ Available water storage values greater than five inches are common along perennial, intermittent, and ephemeral surface water features like Ciénega Creek and Babocomari River. Areas with values less than two inches occur in the northeastern, southeastern, southwestern, and northwestern parts of the AVA.

Available water storage represents the amount of water soil can store, in this case in the top approximately 40 inches (1 meter), for plants. As a characteristic of vineyard soils, it influences how much rain, melted snow, and irrigation can be absorbed as well as irrigation frequency.

¹ Gridded Soil Survey Geographic (gSSURGO) Database for Arizona, United States Department of Agriculture, Natural Resources Conservation Service, July 2020 Release. Not all areas have complete or available data.

Soil pH is between 8 and 9 for many areas in the central and north-central parts of the Sonoita AVA.¹ Areas with pH between 7 and 8 co-occur in these parts of the AVA along perennial, intermittent, and ephemeral surface water features like Ciénega Creek and Babocomari River, as well as along the east-central and southwestern AVA boundaries. Isolated areas with pH between 6 and 7 appear in the central part of the AVA, in addition to more widespread areas in northeastern, southeastern, and northwestern parts.

Soil pH reflects the relative acidity (values less than 7) or alkalinity (values greater than 7) of soil. As a component of vineyard soils, it influences nutrient availability, which affects root, canopy, and fruit growth.

¹ Gridded Soil Survey Geographic (gSSURGO) Database for Arizona, United States Department of Agriculture, Natural Resources Conservation Service, July 2020 Release. Not all areas have complete or available data.

For much of the Sonoita AVA, elevations are between 4,500 and 5,500 feet (1,372 and 1,676 meters).^1,2 Higher elevations, some of which exceed 7,000 feet (2,134 meters), occur in the northwest, northeast, and southeast parts of the area.

Elevation creates pronounced differences in temperature and precipitation. Average temperatures at higher elevations are cooler than those at lower ones. Average precipitation amounts at higher elevations are greater than those at lower ones.

¹ US Geological Survey, 1 arc-second (approximately 30 meters) digital elevation model
² relative to the North American Vertical Datum of 1988 (NAVD 88)

The north-central, northeastern, and central parts of the Sonoita AVA mostly have slopes less than 5%.¹ Slopes for much of the east- and south-central parts are between 5% and 30%. Areas along the western and southern boundaries commonly have slopes greater than 30%.

Slope represents the change in elevation across an area. It can influence the amount of sunlight directly reaching vines and thus temperatures within a vineyard, as well as cold-air drainage, water infiltration, soil erosion, and use of vineyard equipment.

¹ US Geological Survey, 1 arc-second (approximately 30 meters) digital elevation model

Many areas across the north-central, central, and east-central parts of the Sonoita AVA face north or east.¹ Much of the northeastern area faces south or west, as do areas in the far southeast and along the western boundary.  

Aspect is the cardinal direction that a slope faces. Like slope, it can modulate sunlight that directly reaches vines and thus temperatures within a vineyard. Locations with south- and west-facing slopes experience higher values of these environmental conditions.

¹ US Geological Survey, 1 arc-second (approximately 30 meters) digital elevation model

Ciénega Creek, Babocomari River, and Sonoita Creek drain out of the Sonoita AVA to the north, east, and west, respectively.³ Turkey Creek drains into the southern part. Much of the AVA is dissected by ephemeral streams.

Natural features that are perennial, intermittent, or ephemeral and engineered features like canals, ditches, and reservoirs make up surface water. In addition to directing water across a landscape, these features can channel cooler air from higher elevations to lower ones on nights with little to no wind, influencing spring and fall freeze risk as well as diurnal temperature range during summer.

³ US Geological Survey, National Hydrography Dataset