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The Role of Chiles Valley’s Climate on Grape Growing

During winter, it is not unusual for overnight temperatures to drop under 20 degrees Fahrenheit. Snowfall is common at higher elevations along the ridges.

In early spring, temperatures are still quite cold in Chiles Valley compared to most other sub-AVAs in Napa. Even though budbreak occurs two or three weeks later than surrounding areas, vineyard managers still have to contend with spring frosts.

During summer, Chiles Valley has sunny days that are occasionally cooled by afternoon fog. Summer fog from the San Pablo Bay and Pacific Ocean does not affect most areas in the eastern hills of Napa Valley because these regions are too protected and elevated. Chiles Valley is an exception to this rule. While Pope Valley does not get fog during summer, Chiles Valley does.

However, this fog has to travel 30 miles to reaches Chiles Valley and it gets there more sporadically than it does the adjacent AVAs on the Napa Valley Floor. The fog that does advance into the region does so later in the day than the majority of the Napa. 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.

In Napa, morning fog generally burns off quickly by the late morning or early afternoon causing temperatures to rise substantially. Chiles Valley does not experience this quick heat build-up that much of Napa does. The fog dissipates slower and the temperature increase is more methodical than it is in Napa. During the growing season, the day time high temperature is reached a few hours later in Chiles Valley than it is in most other parts of the Napa Valley AVA.

At the same time, the climate in Chiles Valley stays moderate later into fall. This allows grapes a couple extra weeks on the vine to develop before harvest. 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.

Chiles Valley runs northwest to southeast and is exposed to northwesterly winds. Additionally, adjacent canyons that run roughly east to west allow breezes into the region. Each afternoon, the northwest opening of the valley acts as a funnel for wind. In combination with the region’s elevation, these winds decrease humidity in the vineyards. Because dry air cools quicker than moist air, the temperature of Chiles Valley decreases quickly when the sun goes down.

During winter, it is not unusual for overnight temperatures to drop under 20 degrees Fahrenheit. Snowfall is common at higher elevations along the ridges.

In early spring, temperatures are still quite cold in Chiles Valley compared to most other sub-AVAs in Napa. Even though budbreak occurs two or three weeks later than surrounding areas, vineyard managers still have to contend with spring frosts.

During summer, Chiles Valley has sunny days that are occasionally cooled by afternoon fog. Summer fog from the San Pablo Bay and Pacific Ocean does not affect most areas in the eastern hills of Napa Valley because these regions are too protected and elevated. Chiles Valley is an exception to this rule. While Pope Valley does not get fog during summer, Chiles Valley does.

However, this fog has to travel 30 miles to reaches Chiles Valley and it gets there more sporadically than it does the adjacent AVAs on the Napa Valley Floor. The fog that does advance into the region does so later in the day than the majority of the Napa. 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.

In Napa, morning fog generally burns off quickly by the late morning or early afternoon causing temperatures to rise substantially. Chiles Valley does not experience this quick heat build-up that much of Napa does. The fog dissipates slower and the temperature increase is more methodical than it is in Napa. During the growing season, the day time high temperature is reached a few hours later in Chiles Valley than it is in most other parts of the Napa Valley AVA.

At the same time, the climate in Chiles Valley stays moderate later into fall. This allows grapes a couple extra weeks on the vine to develop before harvest. 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.

Chiles Valley runs northwest to southeast and is exposed to northwesterly winds. Additionally, adjacent canyons that run roughly east to west allow breezes into the region. Each afternoon, the northwest opening of the valley acts as a funnel for wind. In combination with the region’s elevation, these winds decrease humidity in the vineyards. Because dry air cools quicker than moist air, the temperature of Chiles Valley decreases quickly when the sun goes down.

> Chiles Valley Wineries

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