40°C Days in McLaren Vale: How Vineyards Are Coping
Heatwaves are becoming a defining feature of the growing season in South Australia. When McLaren Vale pushes past 40°C, it’s not just uncomfortable - it’s a critical moment for the vineyards shaping some of the best Grenache in McLaren Vale.
At Aphelion, we work closely with long-term growers across the region, including Brini and Wait vineyards in Blewitt Springs and Hickinbotham in Clarendon, sites widely regarded among the best vineyards in McLaren Vale for Grenache.
Right now, these vineyards are in a particularly sensitive phase of the season: berry formation, edging closer to veraison (when the berries begin to change colour and soften), which we expect to begin within the next two weeks. It’s a moment where balance, restraint and experience matter more than ever.
What Extreme Heat Does to Grapevines
Once temperatures rise above around 35°C, grapevines begin to experience heat stress. At 40°C and above, normal vine function can slow significantly:
- Photosynthesis reduces as vines close their stomata to conserve water
- Leaves and berries can overheat, particularly if fruit is exposed
- Berry development may stall or become uneven if stress is prolonged
- In severe cases, sunburn or shrivel can occur
Heat itself isn’t the enemy.
Managed carefully, short periods of stress can help control vigour and build concentration.
The key is thoughtful, site-specific management.
Berry Formation to Veraison: A Critical Window
We are currently in the bridge between flowering and veraison - a period where berries are forming, beginning to soften and preparing for the colour change that signals the start of ripening.
Veraison is one of the most important transitions of the growing season, particularly for Grenache. In the lead-up, vines are highly sensitive to both water stress and heat spikes, making decisions during heatwaves especially consequential.
How Our Growers Are Managing the Heat
Across Blewitt Springs and Clarendon, vineyard teams are making daily - sometimes hourly - decisions based on weather forecasts, soil moisture, canopy condition and vine behaviour.
Irrigation with Intent
Water is applied strategically, not reactively:
- Timed for early morning or evening to avoid thermal shock
- Used to support transpiration so the vine can cool itself naturally
- Prioritised block by block depending on slope, soil and exposure
In Blewitt Springs, sandy soils drain freely, demanding precision. In Clarendon, deeper soils provide buffering but still require careful monitoring during prolonged heat.
Note- the Wait vineyard is dry grown, so is never irrigated.
Canopy as Natural Protection
Leaf cover plays a crucial role during extreme heat:
- Selective leaf removal is delayed or avoided on the hottest side of the row
- Canopies are shaped to balance airflow with shade
- Fruit zones are protected from harsh afternoon sun
Soil Health and Ground Cover
Healthy soils help moderate temperature extremes:
- Ground cover and mulch reduce reflected heat
- Improved moisture retention protects the root zone
- Living soils improve vine resilience across heat events
The Importance of Site: Blewitt Springs & Clarendon
Not all heat is experienced equally in McLaren Vale.
- Blewitt Springs offers elevation, sandy soils and cooling breezes, alongside fast drainage that requires constant attention
- Clarendon brings altitude, structure and soils that retain moisture longer, while still needing protection during extreme days
Our growers at Brini, Wait and Hickinbotham understand these nuances intimately. This deep site knowledge is a key reason these vineyards consistently produce some of the best Grenache in McLaren Vale.
Long-Term Adaptation to Heat in McLaren Vale
How are McLaren Vale growers adapting to more frequent heatwaves?
As extreme heat events become more common, growers are evolving their practices through:
- Investment in more efficient irrigation systems
- Adjusted canopy architecture for warmer seasons
- Improved soil health to increase moisture retention
- Variety and rootstock choices better suited to Mediterranean climates
Does extreme heat reduce wine quality?
Not inherently. Heat requires careful management, but when handled well it can produce wines of depth, balance and character. The difference lies in timing, restraint and experience.
Why Days Like This Matter
The wines we release in years to come are shaped by days like today - by early starts, late finishes, and countless small decisions made under intense conditions.
If you enjoy wines that reflect place, season and human judgement, this is where that story begins.
Discover the Wines Shaped by This Season
Our current releases reflect the vineyards and growers behind them - from Blewitt Springs to Clarendon.
Explore the Aphelion range, join our Wine Club, or enquire about corporate gifting via the Aphelion website. Join the email list if you’d like to hear more about what’s happening in the vineyards as we move into veraison. If you’d like recommendations or details, comment or email Lou and I’ll send them through.
Louise Rhodes Mack
Founder & Creative Director
Aphelion Wine Co.
