Temecula Valley

Geological Influences

Temecula Valley’s location in perennially warm Southern California, at the border of northern San Diego County and southwestern Riverside County, ensures plenty of ripeness in the vineyards. But the key to the region’s favorable Mediterranean climate is its proximity to the Pacific Ocean. The valley runs west to east, starting only 22 miles (35 km) from the coast.  Two low gaps—principally the Santa Margarita Gap and to a lesser extent the Rainbow Gap—in the intervening mountain range allow the cool marine air through, for the low nighttime temperatures critical to retaining acidity in the fruit and freshness in the wine. During the growing season, the warm air in the Coachella Valley to the east rises, creating a vacuum effect that pulls in westerly breezes with a strong cooling effect. In addition, a cool mist famously lingers at about 1,400 feet (427 m), aiding moisture retention.

Mountains/River/other key influences

Temecula Valley is surrounded by significant mountains, rising from 2,000 to 11,000 feet (610-3,353 m) above sea level. The higher-altitude, colder air that collects between the peaks at night flows down into the valley, joining the marine layer from the ocean and magnifying the cooling effect. The vineyards are generally planted on the lower benchlands, at 1,200 to 1,600 feet (366-488 meters), taking advantage of the lower-elevation daytime warmth and the flow of cool air at night. The region’s southerly latitude gives it a slightly higher angle to the sun and greater solar intensity than in Northern California’s growing regions. It also receives relatively little rainfall, which, along with the warmth and solar intensity, results in an early growing season—generally running from March through September.

Soil Diversity

The soils in Temecula Valley are primarily decomposed granite, offering well-draining, sandy loam soils on the slopes, where most vineyards are planted.

Climate

Temecula Valley enjoys a Mediterranean climate, thanks to its proximity to the Pacific Ocean. As daytime temperatures surge in the inland valleys to the east, and the warm air rises, the cooler, heavier marine air is drawn inland. Two low places in the Coastal Mountain Range—the Santa Margarita Gap, most importantly, and the Rainbow Gap to a lesser degree—allow the cool air through, directly into Temecula Valley, moderating daytime temperatures and slowing ripening enough to allow grapes to develop complex flavors as sugar levels rise. Rain seldom interrupts the season and the process.