Climate

This table of weather data for the last thirteen years is from the Washington State University Public Agricultural Weather Service (PAWS) station located 5 miles south of the vineyard site. Temperatures at Stone Tree tend not to fall quite as low as the Mattawa PAWS station at night, and usually are not quite as high during the day.

Year Max Air Temp (F) Min Air Temp (F) Avg Air Temp (F) Total Precip (In) Total Etr (In) Total Eto (In)
1989 98.53 -2.92 52.03 7.07 55.83 52.65
1990 105.37 -7.78 53.27 3.32 57.86 55.22
1991 101.7 5.9 52.62 5.65 57.42 54.71
1992 106.29 6.26 53.84 6.11 57.87 54.91
1993 99.59 -1.12 50.14 5.71 55.57 52.94
1994 106.27 5.18 54 4.83 63.22 60.01
1995 98.91 9.14 52.58 9.58 54.48 52.02
1996 106.14 -17.5 50.07 7.2 54.72 51.29
1997 100.42 11.3 52.65 6.2 53.19 50.88
1998 108.32 1.78 54.57 4.7 55.6 52.71
1999 102.2 20.37 53.41 3.46 57.32 55.23
2000 102.97 8.55 51.73 5.21 55.01 51.4
2001 103.86 15.49 53.3 5.84 57.9 54.34
2002 105.75 14.56 53.31 3.92 55.49 51.71

Precipitation on the Wahluke Slope, averaging just 6 inches per year, is at the low end of the range for eastern Washington. The temperature extremes shown in this table are typical for most of eastern Washington.

Growing Season

This figure illustrating the mean length of the growing season throughout the state of Washington, shows the Wahluke Slope to average 200 or more frost-free growing days. The location of the vineyard is the yellow/red dot on the southern tip of Grant County.

Length of Growing Season in Washington State

From Washington Viticulture – The Basics in Growing Grapes in Eastern Washington Proceeding from a Washington State short course on establishing a vineyard and producing grapes. Page 13. Good Fruit Grower. 1998

As can be seen from the map, the chosen site has one of the longest growing seasons in the state.

Heat Accumulation

This figure illustrates the distribution of accumulated heat units throughout the state of Washington. Stone Tree Vineyard lies within the 3500 Heat Units circle north of Benton County.
Distribution of Heat Units in Washington State

From Washington Viticulture – The Basics in Growing Grapes in Eastern Washington Proceeding from a Washington State short course on establishing a vineyard and producing grapes. Page 14. Good Fruit Grower. 1998

Here is a graph of Base 50 heat Units from the PAWS site for 2002 for the Benton City, Mattawa, and Walla Walla weather stations:

It can be seen that Mattawa is very slightly less warm than Benton City, and much warmer than Walla Walla. With our 5 – 10% slope we are probably somewhat warmer than the Mattawa PAWS site.

Winter Temperatures

This figure illustrates the contours of Extreme Minimum Temperature throughout the State of Washington. The location of Stone Tree is the yellow/red dot on the map.
Extreme Minimum Temperature in Washington State

From Washington Viticulture – The Basics in Growing Grapes in Eastern Washington Proceeding from a Washington State short course on establishing a vineyard and producing grapes. Page 15. Good Fruit Grower. 1998

Temperatures below –14 F are lethal to vinifera grapes. No grape growing region in Washington is immune to vine-damaging extreme low temperatures.

Aspect

The Stone Tree site slopes from 950 feet up to over1200 feet above sea level over a 4000 foot distance, for an average slope of approximately 8%.

Stone Tree Vineyard Site Topography


The North-South aspect allows for optimal solar gain. North-South row orientation maximizes this effect.

Cold air drains naturally down the slope of the vineyard to the south and into a basin at an elevation of 800 feet above sea level. The effect is a significant reduction of the risk of crop loss due to spring and fall frosts.

During the “Halloween Frost” of 2002, the temperature at the lowest point of our site was 14 degrees Fahrenheit. Other locations on the Slope reached as low as 8 degrees Fahrenheit.

Wind Conditions

Winds are predominantly from the West and Southwest, and average 8 -12 mph in late summer afternoon. Frequently, winds shift and blow down-slope from the north, the same direction as the row orientation, which has a number of beneficial effects. Winds can gust higher, but so far have not been severe enough to damage vines.