Early Budburst Prolongs the Risk of Late Frosts
This extends the period in which the young buds and shoots have to survive the danger of frosty nights, which are not uncommon in April. The risk of late frost is generally only averted after the "Ice Saints" on May 15th. This refers to the feast days of three saints - St. Mamertus, St. Pancras and St. Serbatus, which in the northern hemisphere fall between May 12-15, and often coincide with the last frosts of spring.
In the Sachsen winery Schloss Wackerbarth, frost protection candles and controlled fires were lit in vulnerable vineyards on the night of April 14 after the meteorologists had predicted that the temperature would drop to minus two degrees. This allowed the air to be heated to above zero degrees.
Temperatures just below zero degrees Celsius can inflict long-lasting damage on new growth. This was most recently seen in Germany on April 20, 2017, when, after a similar early budburst in all growing regions, severe frost damage led to nationwide harvest losses of 17 percent compared to the ten-year average.