The Powerful Effect of Weather on the Wine Year

The interaction between the weather and the wine year is one of the most intriguing elements in wine production.

The weather plays such an integral part in the final product, tomes have been published about the grape’s interdependency on weather patterns.

It seems that every day we are hearing reports about the effect in our world of climate change. The most recent sizzling temperatures on continental Europe had me remembering of their impact on the development of grapes and the ultimate flavours of the wine we drink.

We all know that flavour is largely determined by the grape itself, as well as, colour, sugar, acidity and the levels of tannin in the wine. Other conditions, namely climate, weather, sunlight, water, warmth and nutrients also affect the taste of the wine.

So, what effect does a warming planet, unpredictable weather cycles, and increasing wet vs. dry rain/drought cycles have on the ultimate taste of the final product, during the wine year.

That’s what I want to write about in this post.

We all know that flavour is largely determined by the grape itself, as well as, colour, sugar, acidity and the levels of tannin in the wine #greenacresirl
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What is the Wine Year?

First of all let’s define what a wine year is. The vine is a perennial plant that undergoes an annual cycle of fruit production. It also has a lifecycle of its own that flows from birth through immaturity to full production and tails off into old age.

It is only by digging deeper into the effect of weather on the wine year, that we see how it determines how easy or difficult it is to grow grapes and how flavours can be influenced.

Climate is one of the other conditions I mentioned above. This is a most important factor in influencing a crop for your favourite wines, including quality, productivity, and more.

Read on and I’ll outline a typical vineyard’s activity, month by month and then discuss how weather effects the wines that you taste.

The Wine Year Month by Month.

I’m going to discuss an overview of the classic calendar of vineyard work rather than delve into the various ‘new’ styles being introduced (see my recent post: What’s the Difference between Organic, Biodynamic, Natural and Vegan Wine?). The outline below tells the story of the classic method as practised in France.

January Prune the dormant vines
February Finish pruning
March Vine emerges from dormancy (ploughing)
April Bud-break (+ planting of young vines)
May Combat weed growth + frost + pests
June Flowering
July Combat weeds + trim long vine shoots
Aug Weed + spray + trim excess growth
Sept Begin harvest (night-time for coolness)
Oct Finish harvest + spread manure/fertilizer
Nov Trim long shoots + spray against mildew
Dec Start pruning + tidy up drains/roads/fences etc.

Vines cannot thrive unless they undergo a dormant winter period. This dictates where in the world they can be grown, as dormancy is triggered by cold. This gives rise to the difference between weather and climate.

Weather vs Climate

Basically, the word “climate” refers to the general conditions in a given place over a long period of time, while the term “weather” refers to temporary conditions that might or might not be unusual.

Wine climates suitable for production are broken down into three categories: hot, moderate, and cool, all based on their latitude (closeness to Equator), altitude (the higher, the cooler), and sea influences (warm vs. cool ocean currents).

Wine climates suitable for production are broken down into three categories: hot, moderate, and cool, all based on their latitude, altitude, and sea influences #greenacresirl
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Cooler Climates

In cooler climates and weather, grapes have more difficulty ripening. Less ripe grapes have high levels of acidity, giving them a tart taste which many people perceive as pleasant and refreshing, but others might legitimately find sour and harsh.

These grapes also have lower sugar levels, which results in drier wines with lower alcohol and lighter body. If you like your wines light, crisp, and dry, you might enjoy tasting wines from cooler regions and vintages. The ripeness of grapes is also tied to the amount of sunlight they receive throughout the growing season, regardless of temperature.

That’s one of the reasons prolonged rain can be a problem in some areas – in addition to the lower temperatures often associated with rainy weather, the sunlight is also reduced, leading to grapes with less ripeness.

Warmer Climates

In warmer climates and weather, grapes ripen more easily, leading to lower acidity, higher sugar levels, and darker colour. The higher levels of sugar allow for greater levels of alcohol, which makes the wine more full-bodied.

It’s important to note that higher levels of sugar in the grapes doesn’t mean that wines made from those grapes need to be sweet. You can still ferment sweet grapes into a dry wine, but that wine will have higher levels of alcohol. If you like wines full, soft, and fruity, you might want to try those from warmer climates and vintages.

Weather Conditions, Vintages and the Wine Year.

Vintage is about the last thing regular wine drinkers look for on a label, but it can be a great indicator of what’s going on in the bottle. The best vintages, in any region, have a growing season that’s consistently warm day to day, with cool nights; no frost after budbreak; and rain in the growing season but not during harvest.

In years that deviate from this ideal, the effect is noticeable. Hot vintages can result in higher alcohol levels, very ripe fruit and lower acidity; cold-vintage wines tend to be lighter bodied with higher acidity. If it’s too cold, grapes won’t ripen enough to be made into wine at all.

Most of the wine growers that I know are nearly more obsessed about the weather than meteorologists. They use wind machines, helicopters and the simple bonfire to fend off frost. My heart has gone out to them in recent years as I witnessed them losing a year’s livelyhood, due to weather conditions.

So, what are their worst weather nightmares?

  • Frost. Grapes are vulnerable to frost from the moment of bud break until harvest.
  • Hailstorms. The stones can damage the grapes and shred leaves.
  • Heat Spikes. Rapid temperature changes can cause overripening quickly.
  • Drought. Can make it hard for some vines to reserve carbohydrates.
  • Fog. Fog makes the area stay cooler, and the sunlight cannot penetrate through to help ripen grapes during the day.
  • Late-Season Rains. If rain gets into the grape clusters, they can cause mould and mildew.

Several Periods of the Growing Year are Critical

So, weather conditions have a big say in whether a vineyard is going to be successful in any given year. Vintages vary because several periods of the growing season are critical.

The first is spring, when frosts can damage the tender buds, as late as May. Flowering, in June, establishes the size of the harvest, and its date. July and August can be dangerous if the weather is damp (mould and rot).

Sunshine in September is vital to fully ripen the grapes, and a dry harvest period in September/October allows the fruit to be brought in free from swelling, due to excess moisture.


The tasks of the grape farmer have not changed since winemaking began but the weather patterns and climate have. The classic regulation of growth, fending off weeds, pests and diseases and then harvesting the crop at the right time is now only the start of the current challenges facing those people dedicated to the vine.

For me, understanding all the work and effort that has been put into ensuring I enjoy the experience only adds to the pleasure of opening a bottle of wine.

I hope you agree with me and that this post has provided you with an overview of climate and weather and how they affect the wines you love.

One last thing – did you know that we launched the Green Acres mobile app recently? Now you can bring us home in your pocket. Book tables, browse wines, learn of special offers, check events, connect with us, earn loyalty rewards and much more.  We would really appreciate if you would click on either of the tabs below to download for free.

Talk to you soon, Donal.

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