Climate by region
Merlot
Merlot generally ripens before Cabernet Sauvignon, which makes late-summer warmth and rain during its earlier harvest period especially relevant.
Regional figures use 1991–2020 from the combined regional record · updated through Sep 13, 2026.
Climate by region
1991–2020 averages calculated from complete combined regional records.
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| Region | Growing season | Mean temperature | GDD | Rain | Hot days | Harvest rain | Last updated |
|---|---|---|---|---|---|---|---|
| CoonawarraAustralia | Sep 1–Apr 30 | 16.2°C | 1518 GDD | 306.3 mm | 11.7 | 85.4 mm | Aug 20, 2026 |
| Maipo ValleyChile | Sep 1–Apr 30 | 16.5°C | 1596 GDD | 216.3 mm | 0.0 | 56.7 mm | Sep 12, 2026 |
| BordeauxFrance | Apr 1–Oct 31 | 18.0°C | 1718 GDD | 455.4 mm | 2.5 | 189.6 mm | Jul 15, 2026 |
| TuscanyItaly | Apr 1–Oct 31 | 19.0°C | 1930 GDD | 464.9 mm | 0.4 | 231.2 mm | Aug 20, 2026 |
| StellenboschSouth Africa | Sep 1–Apr 30 | 18.4°C | 2023 GDD | 329.4 mm | 0.2 | 98.1 mm | Sep 13, 2026 |
| Castilla y LeónSpain | Apr 1–Oct 31 | 17.5°C | 1639 GDD | 255.6 mm | 26.4 | 88.5 mm | Aug 20, 2026 |
| Napa ValleyUnited States | Mar 15–Nov 15 | 18.4°C | 2086 GDD | 208.8 mm | 13.2 | 71.4 mm | Sep 13, 2026 |
| Walla Walla ValleyUnited States | Mar 15–Oct 31 | 15.0°C | 1320 GDD | 268.9 mm | 6.8 | 76.6 mm | Aug 20, 2026 |
| Yakima & Central Columbia BasinUnited States | Mar 15–Oct 31 | 16.4°C | 1586 GDD | 131.7 mm | 14.8 | 38.0 mm | Aug 20, 2026 |
References and alternate names
- Washington State University Viticulture & Enology: growing degree days, base temperature, and season heat accumulation reviewed 2026-08-14
- Australian Wine Research Institute: heatwaves and their effects on grapevines reviewed 2026-08-14
- UC IPM: Botrytis bunch rot, late-season moisture and rot risk reviewed 2026-08-14
- VIVC cultivar passport: Merlot Noir (Merlot) reviewed 2026-08-11
Search recognizes the alternate names listed above.