Saint Helena Appellation Climate: Warm, due to greater protection from western hills, with less fog or wind incursions. This narrowest part of the Napa Valley floor floor provides more heat reflection off the hillsides. Mid-summer temperature peak is often in the 85 -90Â°F range (30 to 35Â°C).
Elevation: 150 to 5 00 ft. (46 to 152 m).
Rainfall: 38 to 40 inches (95 to 101 cm) annually.
Soils: South and west borders are more sedimentary, gravel-clay soils, with lower fertility and moderate water retention. Further north and to the east soils are prevalently volcanic in origin and are deeper and more fertile.