WSU Viticulture and Enology

Research and Extension

Grapevine Cold Hardiness

Real-Time Cold Hardiness Monitoring

Critical temperatures for wine and juice grapes are determined using a method called “differential thermal analysis” as described by Mills et al. (2006).  These data are updated approximately weekly from mid-October through mid-April. Data is collected from buds and canes (node positions 4-7) on mature vines grown at the WSU Irrigated Agriculture Research and Extension Center (5 miles north of Prosser, WA) and from nearby commercial vineyards.

This information is provided as a service by WSU with partial funding from the Washington Association of Wine Grape Growers through the Washington Wine Industry Foundation and the Washington State Concord Grape Research Council. WSU is not responsible for any damage  or loss resulting from the use or misuse of this information.

How do use this Table: Click on a variety name to open its seasonal cold hardiness graph.

**Note: Cold temperatures in November 2014 resulted in minor to moderate levels of primary bud damage in a few varieties (e.g., Semillon, Pinot noir, Barbera, Zinfandel, Sangiovese). As such, the reported numbers here are the bud temperature thresholds for surviving buds only. Due to this cold snap, we recommend checking buds prior to making pruning decisions.

Bud and cane exotherms can no longer be determined for the varieties in red below because they are very rapidly approaching bud swell.


Date Variety BUD10
3/30/15 Merlot
3/3015 Syrah
3/23/15 Chardonnay
Cabernet Sauvignon
3/19/15 Sangiovese
3/19/15 Nebbiolo
3/26/15 Zinfandel
3/26/15 Petit Verdot
3/26/15 Lemberger
3/26/15 Grenache
3/19/15 Pinot noir
3/18/15 Auxerrois
3/18/15 Sauvignon blanc
Pinot Gris
3/24/15 Semillon
3/25/15 Muscat blanc
3/25/15 Green Veltliner
3/25/15 Chenin blanc
3/25/15 Alvarinho
3/27/15 Concord

                                    Last updated by Lynn Mills on Mar 31, 2015 at 11:00 AM                                


Interpreting the Graphs and Table


Click image for a larger version.

Click image for a larger version.

BUD10 is the temperature at which 10% of the primary buds will be killed; BUD50 and BUD90 refer to 50% and 90% bud damage, respectively. PHL10 is the temperature at which 10% of the phloem (bark) is damaged or when cane damage is starting. XYL10 is when phloem damage is complete and xylem (wood) damage is starting. This would be considered severe cane damage. Grapevines can survive more than 50% phloem damage and still be productive. When xylem becomes damaged, grapevine productivity and survival can be compromised.

If the temperature lines in the graph (top two blue lines) cross over the critical temperature lines for buds, then damage has likely occurred. Please review the Resources in the right navigation bar for information on managing cold-damaged vineyards.

Now that we are beginning to observe the range of development between first swell to full swell in the different varieties, the following guideline might be helpful. 

As we approach bud break, we will not be able to run exotherm analysis in grapes much longer.  It is already impossible to determine bud exotherms in some varieties.  In previous years we have included the critical temperatures for several different varieties during the period leading up to bud break.  Since every variety responds differently to cold, this should be used only as a rough guideline.  In April of 1997 we ran some freezing tests on grape buds and canes at different phenological stages and found the following:

  • Cabernet Sauvignon at first swell sustained no damage down to 25 F.
  • Merlot at full swell showed slight damage to the buds, phloem, and xylem at 25 F.  More serious damage to the phloem and xylem occurred at 23 F. 
  • Chardonnay at bud break showed slight damage to the buds and phloem at 27 F. More serious phloem and xylem damage occurred at 25 F.  Buds were seriously affected at 24 F.
  •  Interlaken at first leaf stage sustained cane damage at 28 F and leaf damage at 26 F. Both cane and leaf damage became serious at 25.



Cold Hardiness Model

Washington State University has developed a Cold Hardiness Model to predict grapevine cold hardiness anywhere temperature data is available. It is available both as an EXCEL sheet (to enter your own weather data), or via AgWeatherNet (for WA locations).

More information on Cold Hardiness Modelling is located at:


Cold Hardiness Modelling

Preventing Cold Damage in Grapes:

Assessing Cold Damage in Grapes:

Responding to Cold Damage in Grapes:

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