The problem is getting worse
The risk of late frost damage will continue to increase in the coming years, because the date on which late frosts occur remains the same for most grape varieties, which tend to sprout earlier and earlier. More and more often, green leaves are already developed in the critical phase at the end of April/beginning of May. Only as long as there is no green tissue, however, the vine have a good frost resistance. Once leaves have unfolded and shoots have grown, frost damage occurs even at temperatures just below freezing point. It is therefore advisable to think about protective or preventive measures.
Most frequent: radiation frost
Late frosts can occur above all when an inversion layer develops during high pressure weather. While the air near the ground is normally warmer than the layers above, this is reversed in cold frost nights. Without a protective cloud layer, the warm air rising from the ground can escape upwards. At the same time, cold air flows from the higher altitudes into the valley. This is how the inversion stratification is created: near the ground, the temperature is the coldest and the higher you climb, the warmer the air masses are. In this situation, there is no air exchange by wind, because the cold and heavier air masses are under lighter layers of air. This leads to the dreaded late frost damage.