Local Terroir

Geological Influences

As with most coastal counties in California, the principal geologic influences have been the Pacific Ocean and volcanic activity resulting from tectonic shift. Where the ocean reached inland, the result was deep, sedimentary soils. At the junction of tectonic plates, subduction occurred. That led to volcanic activity, the rise of mountains, and creation of igneous rock, such as granite and gabbro.

In addition to being a source of soils for the valleys, the mountains and hills provide a range of altitudes at which vineyards may be located. The mountains can also shield growing areas from sea breezes and offer various exposures to the sun.

Mountains/River/Other Key Influences

There are no rivers of significance where San Diego County viticulture is concerned.

In San Pasqual Valley, mountains are the source of the decomposed granite soils and provide a range of elevations, resulting in diversity among the vineyards. The mountains have much the same effect in Ramona Valley, but also isolate the valley from fog and some of the Pacific Ocean’s cooling breezes.

Soil Diversity

The soils of San Diego County tend to vary according to distance from the ocean. Areas closest to the ocean have subsoils which are marine sedimentary and are also relatively new. Just east of that zone are some volcanic hills and mountains with igneous subsoils. Moving further east, into the “Western Belt,” which includes the Ramona Valley and San Pasqual Valley AVAs, the soils are alluvial, derived from gabbro and granite eroded from the mountains. Further east still is the “Eastern Belt,” which is more uniformly granitic in origin but includes metamorphic zones. Finally, in the easternmost parts of the county, soils are again sedimentary.

There is, of course, soil variation between the two AVAs, and from one vineyard to the next. But the soils are all based on some form of decomposed volcanic material, especially granite. Soil granularity varies from gravel to clay and the  rate of drainage differs accordingly. However, since rainfall is so low in the region and irrigation is a virtual necessity, drainage isn’t really an important factor for wine quality.


The climate for the majority of San Diego County vineyards is hot-summer Mediterranean. The growing season is dry, sunny, and very long.

During the growing season, daytime temperatures often rise above 32.2° C/90° F. Cooling breezes from the Pacific Ocean regularly lower night time temperatures by -1.1 to 10° C/30-50° F.

Annual rainfall is low. Ramona Valley averages just 419 mm/16.5 inches per year. San Pasqual Valley receives just 330 mm/ 13 inches annually. The sea breezes tend to be dry as well. These factors make water availability for vineyards crucial.

Some vineyards, particularly in San Pasqual Valley, are able to draw water from small streams or wells filled by watersheds. Other vineyards, like the homes around them, rely on water routed in from the Colorado River or desalinated sea water.

As is common in most irrigated regions these days, San Diego County vineyards typically use drip-irrigation to maximize efficiency and prevent over-watering. Water conservation efforts in the county overall have also reduced the impact of California’s ongoing drought. However, water availability will be a continuing area of focus, if not concern.

San Diego County grows more avocados than any other county in the United States. But, in recent years, more than 5,000 avocado trees have been uprooted because the cost of irrigating them was too high. (Water requirements for avocados are about ten times greater than those for grapes.)



San Pasqual Valley is in San Diego County, about 40 km/ 25 miles north by northeast of the city of San Diego. The valley straddles Highway 76 between the communities of Escondido and Ramona.

The valley is surrounded by low mountains to the north, east, and south. On the western side is Lake Hodges, filled by the San Dieguito River which drains the mountain watersheds.

The AVA is bounded by Interstate 15 on the west and the 152-m/500-foot altitude line on its other sides.

Name Background

Records show the area being called “San Pasqual” at least as far back as 1846. A village with the same name existed in the valley in the 1820s, if not before.

Topography/Elevation/Water Sources/Geographic Features

The San Pasqual Valley AVA is on an alluvial plain. Elevations range from between 91 and 152 m/300-500 feet, with varying slopes.

Principal water sources are streams from watersheds which eventually feed into the San Dieguito River.

Geology/Soil Composition

The San Pasqual Valley AVA has substantially uniform alluvial soils.


  • Hot-summer Mediterranean (Csa)
  • Winkler Region III
  • The San Pasqual Valley climate is heavily influenced (moderated) by the Pacific Ocean, just 16-24 km/10-15 miles away.
  • Growing season temperatures rarely rise above 35° C/95°F, dropping to  less than 18.3° C/65° F at night.
  • Annual mean rainfall has averaged 330 mm/13 inches over the past decade, with a minimum of 203 mm/ 8 inches, and a maximum of 406 mm/16 inches.
  • Wind speed averages about 10.5 km/h (6.5 miles per hour).

Main Grape Varieties 

Vineyards in both San Diego County AVAs tend to be planted to several, sometimes many, varieties. Robust red varieties, such as Cabernet Sauvignon, Merlot, Syrah and Sangiovese tend to dominate. But more than 60 varieties are planted overall, including whites ranging from Viognier to Muscat, Chardonnay and Falanghina.


The Ramona Valley AVA is a 36,017-ha/89,000-acre region in central San Diego County. The AVA is northeast of the city of San Diego and southeast of the San Pasqual Valley AVA. Near the center of the AVA is the town of Ramona.

The AVA is rectangular in shape, tilting down to the southwest.

Name Background

In 1886, a small settlement called “Nuevo'' was renamed Ramona by the Santa Maria Land & Water Company which had just purchased substantial land there.

Topography/Elevation/Water Sources/Geographic Features

Nicknamed “Valley of the Sun,” Ramona Valley ranges in altitude from 198 m/650 feet to more than 914.5 m/3,000 feet and thus has long hours of direct sun with no fog and only rare cloud cover. The highest area practical for viticulture is at 804.7 m/2,640 feet.

The highest elevations are on the east in the Cuyamaca Mountains foothills. The lowest are in the southwest, at San Vicente Reservoir, and the west.

The valley is almost entirely surrounded by mountains. Principal exceptions are the reservoir in the southwest and an outlet for Santa Maria Creek in the northwest.

Geology/Soil Composition

The Ramona Valley AVA has fertile soils derived from surrounding mountains of volcanic origin. The soils are well-drained sandy loams atop sandy clay loams. The soil series includes Ramona, Visalia, Las Posas, and Fallbrook.

The fertility of the soils has made Ramona Valley an excellent and important area for growing fruit trees, row crops, and more.


Hot-summer Mediterranean (Csa)

Winkler Region III, 3,470 degree-days (2060° C)

The Ramona Valley AVA is 40 km/25 miles from the Pacific, which moderates the climate. Altitude and mountains, however, mean that the AVA does not receive the maritime fog found in lower areas outside the AVA.

The altitude and relative isolation from the ocean also mean a greater diurnal shift, as much as 10° C/50°F during the growing season.

Annual rainfall is 419 mm/16.5 inches. That’s more than low-lying areas outside the AVA, but less than higher elevations in the mountains.

Main Grape Varieties

Vineyards in both San Diego County AVAs tend to be planted to several, sometimes many, varieties. Robust red varieties, such as Cabernet Sauvignon, Merlot, Syrah and Sangiovese tend to dominate. But more than 60 varieties are planted overall, including whites ranging from Viognier to Muscat, and Chardonnay to Falanghina.


The South Coast AVA is a large region in southern California, covering areas with climates notably influenced by the Pacific Ocean. It  encompasses all of Orange County, plus a swath covering western Riverside and San Diego Counties. The total area is about 466,197 ha/1,152,000 acres.

The northern border of the AVA is the Los Angeles County line. The western boundary is the Pacific Ocean. The southern limit is the Mexican border. The eastern boundary is the San Bernardino County line in the north and, further south, a line intended to identify the limit of coastal influence.

The South Coast AVA includes the smaller Ramona Valley, San Pasqual Valley, and Temecula Valley AVAs in their entirety.

Name Background

The name is descriptive. There are three large coastal AVAs in California: North Coast, Central Coast, and South Coast.

Topography/Elevation/Water Sources/Geographic Features

Topographical and geographical features vary substantially in this large AVA. However, the region’s disparate terroirs all have climatic influence from the Pacific Ocean in common.

Geology/Soil Composition



Warm-summer and Hot-summer Mediterranean

Winkler Regions I-III

Main Grape Varieties

A huge range of varieties exists in this massive AVA, but robust red varieties dominate due to climate.