## 3 Results  
Figure 3 shows the impacts of heatwaves on grapevine yields for each of the selected winemaking regions in Europe. Overall (Figure 3), for all regions, the occurrence of heatwaves will lead to a decrease in yields, with its magnitude increasing along with the heatwave duration. The main differences between these impacts are the maximum yield decrease and the corresponding dates of occurrence of the heatwave vulnerability (heatwave peak, henceforth). Starting with the westernmost regions, for Portugal (Figure 3a-c), all regions reveal a heatwave peak between 1 and 15 July. The region with the strongest decrease in Portugal is Minho, with \(-15\%\) (five heatwave days) to \(-29\%\) (nine heatwave days). Conversely, in the Portuguese region of Alentejo, the impacts will not be so pronounced (\(-12\%\) to \(-17\%\)). For Spain (Figure 3d-f), La Mancha also shows a peak between 1 and 15 July, while for Ribera del Duero and La Rioja, this peak is expected to occur slightly later, between 15 July and 1 August. Regarding the potential impacts on yield, they will be very similar across these three Spanish wine regions, ranging from \(-12\%\) to \(-25\%\). For the French winemaking regions (Figure 3g-k), the strongest impacts will occur in the Loire Valley and Alsace, reaching \(-30\%\), while Rhone will be the region with the lowest negative impacts, with \(-25\%\). All regions will tend to show the heatwave peak for 15 July, except in Champagne, which will occur on 1 August. Owing to their geographical proximity, the Luxembourgish region of Moselle (Figure 3l) and the German region of Mosel (Figure 3m) show  
Figure 2: Illustrative representation of the synthetic heatwave disturbances/pulses during a calendar year, outlining their onset (dates within color bars), duration (color bar width) and intensity (color bar top). The observed temperature time series are represented by the background shaded graph, while the synthetic temperature time series of the heatwave disturbances are indicated at the top of each color bar. very similar impacts. Both regions show peak dates around 1 August and impacts from \(-15\%\) to \(30\%\). Similar results can be observed for Rheinnessen, also due to their fairly identical climatic conditions (Figure 3n). For the Italian regions (Figure 3o-r), the impacts vary from \(-15\%\) and \(-27\%\). All regions will tend to have their peak dates from the 1 July to 15 July. It is worth noting that Emilia-Romagna (Figure 3q) depicts a comparatively narrow curve, which is very concentrated around the peak date. Figure 3: Yield relative difference (in %) between normal years and years with heatwaves, with a duration from five to nine days, in (**a**) Minho, (**b**) Douro, (**c**) Alentejo, (**d**) Ribera del Duero, (**e**) La Mancha, (**f**) La Rioja, (**g**) Bordeaux, (**h**) Loire Valley, (**i**) Champagne, (**j**) Rhone, (**k**) Alsace, (**l**) Moselle, (**m**) Mosel, (**n**) Rheinnessen, (**o**) Piedmont, (**p**) Tuscany, (**q**) Emilia-Romagna and (**r**) Sicily, depending on to the date of onset of the heatwave. Figure 4 shows a comparison of the peak dates over the 18 selected winemaking regions in Europe. The heatwave peak dates occur before 1 August (inclusively) for all regions. Minho (Portugal), Alentejo (Portugal), Rhone (France), Piedmont and Emilia-Romagna (Italy) reveal stronger heatwaves earlier in the year than other regions. Conversely, La Rioja (Spain), Champagne (France), Moselle (Luxembourg) and Mosel (Germany) will experience stronger impacts when heatwaves occur later (1 August). It should be noted that the regions where the strongest impacts of the heatwaves tend to occur earlier/later are also the regions with the highest/lowest annual mean temperatures (warmer/cooler climates). Figure 5 provides a comparison across all regions of the highest and lowest decrease in yields at each peak date. This assessment was based on the heatwave peak date for each region. The results suggest that the most affected regions are the Loire Valley, Alsace and Bordeaux.