California is the source for nearly all commercially grown domestic grapes, supporting massive agricultural output for both fresh fruit and wine production. The concept of a single “grape season” is misleading because the harvest is a prolonged, staggered process spanning many months across the state’s diverse climates. This continuous availability results from coordinated cultivation across different regions, extending the period when fresh grapes are available from late spring into the winter months. The timing of the season is governed by distinct agricultural schedules for the two primary types of grapes grown.
Understanding the Two Seasons: Table Grapes Versus Wine Grapes
The term “grape season” in California encompasses two separate harvest windows for two distinct products: table grapes and wine grapes. Table grapes are cultivated specifically for fresh consumption; they are bred to be large, crisp, and often seedless, with relatively thin skins. The vast majority of these fresh grapes are grown in the warm, arid conditions of the Central Valley and the Coachella Valley.
Wine grapes, in contrast, are smaller, possess thicker skins, and are intensely concentrated in flavor and sugar content, making them unsuitable for eating fresh. These grapes are grown in a much wider array of microclimates, including coastal appellations like Napa, Sonoma, and the Central Coast, as well as the Central Valley. Because they are destined for processing rather than immediate sale, the timing of their harvest is determined by different scientific metrics.
Calendar of Availability for California Table Grapes
For the general consumer, the California table grape season provides a long window of availability, beginning in May and lasting through January. This lengthy season is made possible by a sequential harvesting approach that moves geographically from the warmest southern regions northward. The earliest grapes appear in mid-May from the Coachella Valley, where the warmer climate accelerates the ripening process.
Once the Coachella season concludes around mid-July, the focus shifts to the San Joaquin Valley, which accounts for approximately 85 percent of the state’s table grape production. The San Joaquin Valley sustains the bulk of the domestic supply through the summer and fall. Early-season varieties harvested in July and August include popular types like Flame Seedless (red) and Ivory (green).
As the season progresses through September and October, mid-season varieties such as the deep-red Ruby Seedless and various black seedless grapes become widely available. The late season, extending into November and December, features robust, storage-friendly varieties like the large Red Globe and Autumn Royal. These grapes are harvested and kept in cold storage, allowing fresh California grapes to be sold well into the New Year.
The Wine Grape Harvest: Timing the California “Crush”
The harvest for wine grapes is an industrial process known as the “Crush,” typically beginning in late August and continuing into October. Unlike table grapes, which are harvested for texture and sweetness, wine grapes are picked based on a precise chemical balance between sugar and acidity, measured in degrees Brix. The ideal Brix level ensures the resulting wine has the proper alcohol content and flavor profile.
The timing of the Crush is highly dependent on the grape varietal and the growing region’s specific climate. Cooler, coastal regions like the Central Coast and Napa Valley often see the earliest harvests for white varietals, such as Chardonnay and Pinot Noir, sometimes beginning in late August. These regions are prized for their slower ripening process, which helps retain the grapes’ delicate acidity.
Inland regions, particularly the Central Valley, generally harvest large volumes of wine grapes later in September and throughout October. The hotter climate in these areas can accelerate sugar accumulation, requiring careful monitoring to prevent the grapes from becoming overripe. Varietals also ripen at different speeds, with Cabernet Sauvignon often being one of the last to be picked, extending the Crush period into late October or even November.
Climate Variables That Shift the Grape Season
The annual schedule for both table and wine grapes is not rigidly fixed but is subject to significant shifts based on yearly weather patterns. Variations in temperature and precipitation can advance or delay the entire season by several weeks. For example, a prolonged cool spring can delay budbreak and subsequent flowering, pushing the entire harvest later into the fall.
Conversely, an increasing frequency of heat events, where temperatures exceed 35 degrees Celsius, can accelerate sugar development but negatively impact the grapes’ quality. These heat spikes can disrupt the ripening process for wine grapes, causing the vines to shut down and potentially leading to earlier harvests. Furthermore, early seasonal rains pose a threat, as moisture can cause ripe grapes to split or encourage the growth of mold, forcing growers to pick ahead of schedule.