Home | Wine Regions | AVA GIS | Data Descriptions | Help | About | Contact



Climate exerts the most profound effect on the ability of a region or site to produce quality grapes. With the exception of low rainfall, which may be offset by intense irrigation, most climatic variables are impossible or cost prohibitive to control.Climate can be considered at 3 different scales in any discussion about viticultural areas: the macroclimate, the mesoclimate, and the microclimate.

Macroclimate refers to the prevailing climate or broad weather patterns of a relatively large area or geographic region. The mesoclimate is a more localized and specific climate, often influenced by topography. The microclimate of a vineyard describes the specific environment from the soil into the vine canopy.

The climate variables critical to wine grape growing and necessary in the description of the Texas wine regions include daily maximum temperature (TMAX), daily minimum temperature (TMIN), daily average temperature (TAVG), annual precipitation (PPT), growing degree-days (GDD), ripening period mean temperature (RPMT), and solar radiation (Rs).


Temperature is most significant in the months prior to ripening and plays a large role in the style of the wine production. The great wine regions tend to be characterized by low diurnal fluctuations in temperature around harvest. In general, minimal variations in temperature around the mean imply greater grape flavor, aroma and pigmentation at given maturity levels. Growing season temperatures play a critical role in description of a viticultural area due to the influence on grape ripening and fruit quality. Vine growth is optimized by average temperatures of 73.4-77ºF.


Lack of adequate rainfall can be of severe influence on grape productivity in the absence of good quality water for irrigation. The adequacy of a total or complete season rainfall for grapevine growth is an obvious climatic criterion. Too much rainfall can be a problem and most quality wines are produced in regions where the annual rainfall does not exceed 70-80cm. Moisture availability at particular growth stages has important implications, thus it is the timing of the excess rainfall that is of greater consequence than the amount of the rainfall.

Growing Degree Days

Growing season temperature is another critical aspect of climate for successful grapevine growth as it plays a crucial role in grape ripening and fruit quality. Growing degree days (GDD) is a measure of growing season temperature and can be used to compare an area's climate with that of a known winegrowing region. Degree-days are a rough measure of the cumulative amount of functional heat experienced by grapevines during a growing season defined as April 1st through October 31st. GDD is determined by subtracting 50 oF (10ºC) from the mean daily temperature and calculating the cumulative sum through the growing season. This base of 50 oF is used in calculations because virtually no shoot growth occurs below this temperature. Cumulative Growing Degrees days is the summation of the individual GDD values for each month in the growing season (April 01st to October 31st).

Ripening Period Mean Temperature

This refers to the average mean temperature during the final ripening months of July through September with temperatures ranging from 15-21ºC (59-69.8 oF). This is often the period during the growing season where rates of acid loss & sugar accumulation determine the potential style and balance of wine.

Data Descriptions


Select a region for description

Bell Mountain
Escondido Valley
Fredericksburg (THC)
Mesilla Valley
Texas Davis Mountains
Texas Hill Country
Texas High Plains

Select a region to enter GIS

Texas High Plains Texas Hill Country Texoma Mesilla Valley Escondido Valley Fredericksburg (THC) Bell Mountain Texas Davis Mountains

The Winegrowing Regions of Texas was created and is maintained by the Knowledge Engineering Laboratory as a component of the Texas Winegrape Network.
Website design by Subodh Prabhu, Elvis Takow, and Ed Hellman
© Copyright 2008 Knowledge Engineering Laboratory