Calistoga AVA – The Big Picture
The Calistoga AVA is known for its topographical diversity and uniform geology with soils created almost exclusively from volcanic activity. Nestled within two mountain ranges, the Calistoga AVA is blessed with a unique terroir for winemaking.
Soils: Primarily volcanic origin with soils ranging from rocky, stony loam on the hillsides, to gravelly loams on the alluvial fans. In the center of the valley floor there are heavier clay-silt soils. Overall, it’s the most geologically uniform of all the AVAs in Napa Valley.
Climate: It’s generally warm to very hot during the day, depending on time of year. During summer months and early fall, the temperatures peak above 100 degrees and drop to the mid-40s at night due to cool afternoon and evening breezes from the Russian River and drawn down mountain slopes. This results in the largest temperature fluctuations (diurnal change) in the valley.
Elevation: Approximately 300 to 1,200 feet.
Rainfall: Averages 22-50 inches on the valley floor but can surpass 60 inches a year.
Soils & Topography of Calistoga
The entirety of the Calistoga AVA is underlain by volcanic bedrock and sediments, making it geologically more uniform that other Napa Valley AVAs with valley floor vineyards. These areas are usually comprised of marine sedimentary rocks on the west side and volcanic on the east side.
On the other hand, Calistoga is topographically more diverse than other Napa AVAs, ranging from steep mountains to valley floor. Unlike most of the other AVAs, the valley floor in Calistoga has very little flat ground, as most of it reflects the slopes of alluvial fans – gentle on the north side and steeper on the south. And its slope and exposure to the sun are quite distinct from that from any other Napa Valley AVAs, providing winemakers with challenges and opportunities in the vineyards.
Climate in Calistoga
The Calistoga region, from valley floor to mountains, is part of a single climatic system characterized during the primary growing season by hot days (which provide color and big berry fruit) and cool nights (which maintain good acid balance for structure and power). These are ideal growing conditions for premium wine grapes.
It’s often assumed that Calistoga has the highest temperatures of any location within the Napa Valley. The hottest single spot in the valley is close to Bale Lane, along the southern boundary of the AVA. Typically though, the hottest areas in the valley run from Stag’s Leap District to south of Dutch Henry Canyon, along the base of the Vaca Mountains.
The Calistoga AVA is cooled by air currents drawn in from the Russian River. These currents are strong enough to support the sailplanes that were headquartered for years at the Gliderport in downtown Calistoga. While daytime peak summer temperatures can reach about 100 degrees at mid-day, the hot air rises and mixes with cooling breezes from the Russian River in the late afternoon until after sunset, cooling the valley floor to about 65 degrees.
In addition, cooling breezes flow down the slopes of both the Vaca and Mayacamas Mountains. On fog-free nights, the cool air moving downslope can bring the temperature down another 12–15 degrees. Rainfall in Calistoga is typically higher than elsewhere, with the highest recorded on Mount St. Helena. Precipitation is highest in the mountains, up to 60-plus inches per year. The valley floor ranges from 20-55 inches.