2013 June Winegrowing Update

Close up images of wine grape clusters and leaves

Winegrowing conditions throughout the month of June were not as dry or windy as in April or May. Mean temperatures and sunlight, however, continued to exceed most recent and historical averages, with the exception of solar radiation in 2012.

Regional mean temperatures eclipsed 10 year averages while also experiencing higher highs and higher lows. June 2013 recorded mean daily temperatures that also exceeded those of 2009 and 2012. Solar radiation exceeded 2009, 2011 and historical averages but failed to reach levels experienced in June 2012. Potentially higher levels of recorded sunlight were diminished by two periods of rare summer rains.

Humidity levels were higher than the historical average for the month of June due to rare and welcomed precipitation. As arid as 2013 has been, June 2013 was still not as dry as June 2012. Wind speeds were calm compared to 10 year historical averages and with 2012 and 2009 averages during June. Only 2009 was slightly less breezy compared with this period in 2013.

The following detailed comparisons attempt to place June 2013’s weather conditions in context with the exceptional vintages of recent past, 2012 and 2009, and the two previous vintage years. You can download the complete report here.



Sonoma Coast / Petaluma Gap Wine Growing Temperature Comparisons

Sonoma Coast / Petaluma Gap Wine Growing Temperature Comparisons

The Petaluma Gap experienced mean daily temperatures that exceeded historical norms during the month of June by 2.33˚F. Diurnal temperature variations were only slightly lower than average, as both high and lows were above 10 year averages by 1.56 and 2.39˚F, respectively.

June mean daily temperatures surpassed those of 2009 and 2012 by an average of 2.3˚F and 2011 by 3.9˚F. Maximum average temperatures were greater than those of 2011 (3.7˚F), 2009 (2.7˚F) and 2012 (1.7˚F). 2013 minimum average temperatures also exceeded all years under review by 3 to 4˚F.

June 2013 experienced similar diurnal temperature variations to 2011 and lesser variations than 2012 by one degree.

Solar Radiation

Sonoma Coast / Petaluma Gap Wine Growing Solar Radiation Comparisons

Sonoma Coast / Petaluma Gap Wine Growing Solar Radiation Comparisons

Solar radiation levels of 645 Ly/Day barely surpassed 10 year historical averages by 9.7 Ly/Day or 1.5% for the month of June. If not for the overcast conditions and minuscule precipitation at the beginning (6/9-10) and end (6/23-25) of the month, we would have experienced another month of higher than usual amounts of sunlight.

Much like conditions in May, June 2013 experienced 40 Ly/Day (6.3%) less solar radiation than 2012 but surpassed 2011 by 52 Ly/Day (8.9%) while barely beating 2009 levels by 9 Ly/Day (5.5%).


Sonoma Coast / Petaluma Gap Wine Growing Humidity Comparisons

Sonoma Coast / Petaluma Gap Wine Growing Humidity Comparisons

Early season arid conditions were met with welcomed, however minor, precipitation in the beginning (6/9-10) and end (6/23-25) of the month which pushed humidity levels higher than average by 2.1% (73%).

June 2013 continued to be drier than 2011 and 2009 by 5% and 1%, respectively. However, 2012 was still drier than 2013 by 6.8%.

Evapotranspiration during June mirrored the previous 10 year average, theoretically returning irrigation demands to historical norms.


Sonoma Coast / Petaluma Gap Wine Growing Wind Comparisons

Sonoma Coast / Petaluma Gap Wine Growing Wind Comparisons

Wind speeds throughout the region were 10.2% lower than the previous 10 year average. Canopy thinning during the early part of June proved necessary to ensure adequate airflow through the fruit zone to alleviate increased fungal/disease pressure due to higher humidity.

June 2013 wind conditions surpassed those of 2011. 2012 and 2009 were windier by 2.8% than June of this year.


Although of supreme importance, weather, in and of itself, is only a single variable in a wine growing season. The resulting fruit quality when it arrives at the winery is determined by a myriad conditions such as timing of weather events, site micro-climates, geography/orientation, training/trellising, fruit set, canopy management, etc etc etc. 

This report is based on Petaluma Gap regional weather data obtained from the California Irrigation Management Information System (CIMIS) Petaluma East Station (144) and is meant to characterize general growing conditions for the region. It should not, in any way, be construed to represent the growing conditions for any one particular vineyard site.