Percentage of grape clusters destroyed by a freak frost that hit the vineyards of Mendoza, Argentina, last week. In some sub regions, 100% of the clusters were obliterated. Vineyards in the Southern Hemisphere are in the process of flowering, the critical time in spring when vines pollinate themselves and are most vulnerable to extreme weather. Temperatures plunged as low as 25 degrees Fahrenheit. In the Mendoza region, up to 25,000 acres were affected.