Climate, Weather & Environmental Influences

Cool, Moderate, and Warm Climates

Climate is the single biggest influence on how a wine tastes, because it determines how much warmth and sunlight grapes receive as they ripen. Wine regions are broadly grouped into cool, moderate, and warm climate categories.

Neither extreme is automatically "better" — climate simply shapes style, and different climates suit different grape varieties and different wine styles.

Maritime, Continental, and Mediterranean Climates

Beyond the simple cool-to-warm scale, wine regions are also described by broader climate types, largely driven by how close they sit to large bodies of water.

• Maritime climates sit near an ocean or large sea, which moderates temperature. Winters stay relatively mild and summers stay relatively cool, with a fairly narrow gap between the warmest and coldest months, and rainfall is often spread through the year. Bordeaux is a classic maritime climate.
• Continental climates sit further inland, away from the moderating effect of the ocean. This produces a much wider annual temperature range, with cold winters and hot summers. Burgundy and much of Central Europe show continental characteristics.
• Mediterranean climates have warm-to-hot, dry summers and mild, wetter winters — the classic pattern found around the Mediterranean Sea itself, as well as in similar climate zones such as parts of California and Chile.

Latitude, Altitude, and Landscape

Several physical features of a vineyard site influence how warm or cool it is:

• Latitude — most of the world's wine regions sit in two bands, roughly 30 to 50 degrees north and south of the equator, where the climate is temperate enough to grow grapes successfully.
• Altitude — temperature drops by roughly 0.6°C for every 100 meters of elevation gained. This is why high-altitude vineyards in warm, low-latitude regions, such as parts of Argentina, can still produce fresher, higher-acid grapes despite being close to the equator.
• Mountains can shelter a vineyard from harsh winds or rain, or, conversely, funnel cooling breezes down onto a vineyard site.
• Slope and aspect — the direction a vineyard slope faces affects how much direct sunlight it receives. In the Northern Hemisphere, south-facing slopes get more sun exposure and are therefore warmer; the reverse is true in the Southern Hemisphere, where north-facing slopes are the warm, sun-exposed ones. Slope also affects drainage and frost risk, since cold air sinks and pools in low-lying areas.
• Soil — while soil composition is explored in far more depth at higher WSET levels, drainage is the key factor here: vines generally perform best in well-drained soils, since waterlogged roots struggle and excess water can dilute grape flavors. Soil color and structure can also affect how much heat is retained and reflected back onto the vines.
• Proximity to seas, lakes, and rivers — large bodies of water moderate temperature, absorbing and releasing heat slowly, can extend the growing season, and may reflect additional sunlight onto nearby vineyards.
• Air movement, fog, cloud, and mist — coastal fog and cloud cover, as seen in regions like Carneros or coastal Chile, can reduce sunlight and keep temperatures cooler; wind can help dry out vineyards after rain, reducing disease risk, though strong wind can also physically damage vines.

Weather Hazards

Alongside general climate, unpredictable weather events pose real risks to a vineyard's yield and quality every year:

• Frost — particularly dangerous in spring, when a late frost can kill young shoots and buds, drastically cutting that year's crop.
• Hail — can shred leaves and destroy or damage bunches within minutes, sometimes wiping out a large share of a harvest.
• Drought — prolonged lack of water stresses the vine and can shut down ripening entirely if severe enough.
• Excess rain — heavy rain, especially close to harvest, can dilute grape flavors, cause berries to swell and split, and sharply increase the risk of fungal disease.
• Extreme heat and sunlight — can scorch or "sunburn" exposed grape bunches and, in severe cases, can halt photosynthesis and ripening altogether.

Every one of these factors — climate type, landscape, and weather risk — combines at a specific vineyard site to determine its overall growing conditions, and ultimately shapes the character of the wine that ends up in the glass.

Putting Site Selection Together

Because so many of these factors interact at once, a single vineyard site can only be properly understood by combining all of them. A slope with excellent south-facing aspect in the Northern Hemisphere might still produce underripe grapes if it also sits at very high altitude in a continental climate with a short growing season; a low-lying, flat site in a warm Mediterranean climate might struggle instead with frost pooling nearby, or with grapes ripening too fast and losing acidity. This is why growers, and the regulatory bodies that define quality wine zones, describe a site's full growing conditions rather than any single factor in isolation, and why identical grape varieties planted in different climates and landscapes can produce such different styles of wine.