Howell Mountains
| Howell Mountains | |
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| (Mt. George Range) | |
Twin Sisters, seen here from Suisun Valley, is the highest summit in the Howell Mountains
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| Highest point | |
| Peak | Twin Sisters |
| Elevation | 2,162 ft (659 m) |
| Geography | |
 location of the Howell Mountains in California
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| Country | United States |
| State | California |
| Counties | Napa County, Solano County |
| Range coordinates | 38°18′24″N 122°10′16″W / 38.3065802°N 122.1710817°WCoordinates: 38°18′24″N 122°10′16″W / 38.3065802°N 122.1710817°W |
The Howell Mountains, which are also known as the Mt. George Range, are one of the California Coast Ranges. They divide the Suisun Valley on the east side, from Napa Valley on the west. Historically the southern part of the range has been referred to as both the Sierra de Suscol (Suscol Hills) and as the Sierra de Napa (Napa Hills).
The Howell Mountains begin at Sulphur Springs Mountain, near the towns of Vallejo and Benicia, and just north of the estuary where the Sacramento River flows into San Francisco Bay. The range then trends to the north and northwest for about 40 miles (64 km) to Howell Mountain, just northeast of St. Helena, California, where it merges with the Mayacamas Mountains. The Vaca Mountains, which are separated from the Howell Mountains by Suisun Valley on the east side, merge with the latter range northeast of St. Helena also. The crest of the range, which culminates at 2,162 feet (659 m) feet in the twin summit of Twin Sisters, represents the divide between the drainage of the Napa River on the west side, and Suisun and Green Valley Creeks on the east. Although Twin Sisters is the high point, both Howell Mountain and Mt. George to the north are better known, due to proximity to grape-growing regions that are popular tourist destinations.
The Howell Mountains have Mediterranean climate with a cool rainy winter, and a warm dry summer with high temperatures up to 100 °F (38 °C) at lower elevations. Average annual rainfall ranges from 40 inches (1,016 mm) per year at Howell Mountain in the north, to 30 inches (762 mm) per year at Mt. George, to 20 inches (508 mm) per year at Benecia in the south. Rainfall is similar on both the west and east sides of the range, with no noticeable rain shadow effect. Because gentle winds blowing inland from the estuary at San Pablo Bay and Suisun Bay are common, hard frosts are very rare, which makes the lower slopes of the mountains ideal for growing grapes, olives and fruit trees.
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Wikipedia