Coombsville AVA, Napa Valley / Cabernet Sauvignon Grape

Total GDD: 3623 (Oct 31)

Day 245 / 245 (100%)

Current Season

Total GDD: 3623 (Oct 31)

Method: 50°F Sine

7-Day Daily Avg: 12.8

7-Day Projection: 3713 by Nov 07

Season: Mar 01, 25 - Oct 31, 2025

Key Freeze Dates (32°F)

Last Freeze:
10%: 01-24
50%: 02-13
90%: 03-13

First Freeze:
10%: 11-23
50%: 11-30
90%: 12-12

Growing Degree Days (GDD) track heat accumulation to predict when plants reach growth stages, pests emerge, and diseases become active.

Thresholds mark specific GDD values when events typically occur, with crossing dates showing when your season reaches each milestone.

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Thresholds & Notes

Budbreak (EL-4) 50 °D

Mar 9, 2025 | Mar 13, 2024 | Mar 17, 2023

Growth Stage

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Bud swell visible. Last frost risk through March 12. Delayed pruning option.

Shoot Emergence (EL-9) 150 °D

Mar 26, 2025 | Mar 24, 2024 | Apr 9, 2023

Growth Stage

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Shoots 2-4 inches. Suckering begins. Coombsville morning fog persists.

12-14 Leaves (EL-19) 350 °D

Apr 15, 2025 | Apr 18, 2024 | Apr 28, 2023

Growth Stage

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Rapid growth phase. First wire positioning. Powdery mildew prevention critical.

Flowering (EL-23) 650 °D

May 10, 2025 | May 12, 2024 | May 25, 2023

Growth Stage

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Cap fall begins. No sprays during bloom. Cool temperatures extend bloom.

Fruit Set (EL-27) 850 °D

May 23, 2025 | May 29, 2024 | Jun 11, 2023

Growth Stage

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BB-size berries. Cluster thinning Coombsville Cabernet blocks. Water management begins.

Bunch Closure (EL-33) 1250 °D

Jun 19, 2025 | Jun 18, 2024 | Jul 6, 2023

Growth Stage

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Berries touching. Leaf removal east side only. Marine influence moderates temps.

Veraison (EL-35) 1750 °D

Jul 19, 2025 | Jul 10, 2024 | Aug 1, 2023

Growth Stage

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Color change begins. Start maturity sampling. Napa Valley heat spike protection.

Harvest - Chardonnay 2250 °D

Aug 15, 2025 | Aug 1, 2024 | Aug 24, 2023

Growth Stage

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22-23° Brix target. Dawn picking Coombsville whites. Natural acidity preserved.

Harvest - Merlot 2650 °D

Sep 3, 2025 | Aug 21, 2024 | Sep 14, 2023

Growth Stage

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24-25° Brix. Soft tannins signature Coombsville style. Hand harvest.

Harvest - Cabernet Sauvignon 3050 °D

Sep 23, 2025 | Sep 9, 2024 | Oct 8, 2023

Growth Stage

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25-26° Brix. Extended hang time possible. Peak complexity achieved.