Washington State University weather

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.

Interpreting the Graphs and Table

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.

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:

Resources