How Does Rain Affect Wine?

How Does Rain Affect Wine?

We are often asked after a solid rainfall season “how did the rain effect the vineyards?”

And it’s a tricky question, because it can be positive or negative depending on timing during the vines growing cycle. We like winter rains—and yet we don’t like rain after berry set (May/June) or too close to harvest. The amount of rain makes a difference depending on the time of year as well. Winter = great. Late Summer and Fall rains = problematic.

To understand this better below are some basic stats to compare Santa Barbara County versus others great growing areas of the world.

Average Rainfall

Santa Barbara County 12-15”

SB County in drought 5-10”

Napa 30”

Oregon 30-40”

France 40”

The good news is we received 18 inches of rain this year and it had a positive impact on our vineyards. When we get adequate amounts of rainfall in the vineyard, the soils and root zone both get flushed of minerals that build up over time that are detrimental to grape vines (salts, magnesium etc.)

In adequate rainfall years, there will be moisture accumulation 15 – 48-inches deep into the soil. This will fill the root zone soil profile. The bulk of grapevine roots, depending on soil type, typically reside in this 15 – 48-inch area. Roots can use that water for a longer period—sometimes into Spring and Summer because they are reaching downward for the water.

In dry years we must supplement with irrigation to try and fill the soil profile. This technique helps but does not replace decent rainfall and roots may be searching in shallow soil for water. This typically requires more irrigation throughout the year.

Normal rainfall gives good shoot (canopy) growth and vines flourish under these conditions. Vines can stress under extreme drought conditions leaving roots/leaves to collapse and struggle to ripen fruit.

When compared to other regions, we need our average rainfall for ideal growing conditions. Other wine country areas, such as France, deal with rainfall all year around and often have the headache of dealing with rain at harvest. Spring rain during bloom can result in poor berry development, lower yields, and erratic ripening. Both spring and summer/fall rain can be detrimental to wine quality due to degradation of fruit.

In contrast, having lower rainfall gives us higher percentage of good vintages because we don’t have to deal with the spring and late season rains. However, our vineyards desperately need our average rainfall years in order to have healthy vines.

So the answer to the question “how does rainfall affect the vineyard?” is: the winter rains are usually beneficial to our growing quality….yet we really don’t like late spring and summer season rains!


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