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What is the climate in Chiles Valley Wine Country like?

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The Chiles Valley Wine Region is located in the Vaca Hills to the east of the Napa Valley Floor. Although the viticultural area is within the broader Napa Valley AVA, it is an entirely separate valley with its own watershed.

One of the more conspicuous aspects of the valley’s climate is its longer than average growing season. Budbreak occurs two or three weeks later than the Napa Valley average. Grapes are left on the vine for a longer time and can therefore develop distinct varietal characteristics.

Zinfandel thrives in the AVA. Sunny days develop sugars while cool winds keep acidity up. The Zinfandels I have tasted from Chiles Valley Wineries tend to be quite fruity with supporting acidity and rounded tannins.

Most fog from the San Pablo Bay is blocked by the western hills of Chiles Valley. Because the fog cover rarely advances above 1500 feet, days are normally sunny. Along with Zinfandel, Sauvignon Blanc and Cabernet Sauvignon are well-suited to the sunny climate.

The fog that does advance into the region does so later in the day than the majority of the Napa Valley. When this occurs, there is less time for the fog to burn off in the daytime sun. The result can be a quick drop in temperatures after the sun goes down.

Because of its relatively sheltered nature, winters are colder and summers are hotter than AVAs on the Napa Valley Floor. During winter, it is not unusual for overnight temperatures to drop under 20 degrees fahrenheit. Vineyards in the AVA can also be succeptible to springtime frosts.

However, Chiles Valley is not entirely protected from external weather patterns and influences. Chiles Valley runs northwest to southeast and is exposed to northwesterly winds. Additionally, adjacent canyons that run roughly east-west allow winds into the region. These winds are an extremely important feature of the valley’s terroir. Depending on the time of year and the hour of the day, the winds can either moderate or exaccerbate temperature patterns. However, an almost constant feature of the breeze is its afternoon/evening duration and cooling effects.

What is the climate in Chiles Valley Wine Country like?

On a hot summer day, the breeze moderates the AVA’s temperature. The afternoon winds also lower the air’s humidity. This causes temperatures to drop more quickly after the sun sets, thus exaccerbating already cold nights.

While temperatures in Chiles Valley are more extreme than the majority of the Napa Valley Floor, they are more moderate than some nearby regions in the Vaca Hills. For example, Pope Valley (not an official AVA) is located to the north at a lower elevation and has higher mountains surrounding it. Because of these characteristics, wind and fog are almost non-existant in Pope Valley. Average temperatures are colder in the winter and hotter in the summer.