The Portuguese heatwave and the resistance of the Távora Valley vines

Oct 21st 22

The historic heat wave that affected Portugal in July subjected the country to extreme temperatures that, in some regions, lasted for two weeks. This situation brought severe challenges for many sectors of the economy, especially agriculture. And certainly winemaking in the Douro Valley. The vines at Quinta do Convento de São Pedro das Águias, in the Távora Valley, displayed drought resistance due to the cooler climate that characterizes the terroir where they grow. 

According to data shared by the Portuguese Institute for Sea and Atmosphere (IPMA), the Pinhão weather station in the heart of the Douro Valley registered on Wednesday, July 13, a new high temperature for that month: 47°C! The following day, July 14, 26 of the 93 IPMA weather stations across the country also registered new record highs. At the same time, the minimum temperatures were also elevated, in some cases over 29 degrees. 

This heat wave was unusual in that it reached further north. Historically, the highest temperatures in Portugal were associated with the south and the Alentejo region. However, this time, the whole of Portugal was characterized by hot days and tropical nights. 

Very high temperatures have a severe impact on the functioning of the grapevines. Firstly, fewer berries can develop (poor fruit set, the physiological accident where the flowers don't develop into fruit), or smaller bunches may form. Secondly, the berries can burn in extreme temperatures, gravely risking production. Finally, drought can also subject the grapevines to water stress resulting in reduced vigour, less fruit or smaller fruit (and even in yellower leaves than usual for the season).

At the Quinta do Convento de São Pedro das Águias they did not experience the burnt fruit incidents recorded in many other regions. Factors such as the altitude and orientation of the vines (primarily facing the north and northeast) contributed to cooler temperatures and fewer hours exposed directly to the sun. The surrounding forest and the way it contributed to the dampness also had a positive impact, above all at the higher levels, where the grapevines displayed more vigour (benefitting from the watercourses from the small springs, which lead to the Távora River).

During the maturation stage, now in August, the month turned out to be very dry and hot, with two more heat waves. The harvest began two weeks earlier than in 2021. Most grapevines could retain the acidity that characterizes the fruit from this terroir, apart from some sections exposed to more water and thermal stress. The harvest took place with the expectation of excellent quality, but production is lower due to the year's constraints.