Meteorologist Samantha Davies

The vineyards in Northern California have been hit by one of the worst frosts in nearly 30 years. Nighttime temperatures at the end of April were in the 20’s. Frost alarms on the vines were set off signaling growers of the freezing temperatures. Frost is not unusual in California, but this season it was particularly bad because of the severity and the duration of the frost. The cold temperatures lasted about twenty nights in a row.

Frost damaged Merlot grapevines are shown at a vineyard in the Stag's Leap Wine District in Napa, Calif. (AP Photo/Eric Risberg)

Growers in Napa and Mendocino are still assessing the damage; it is expected to be in the Millions. It will not be until June until the damage is fully assessed, but growers are expected to have a smaller than average harvest this year.

There are a few things that can be done to prevent frost on the vineyards. Farmers can install wind machines. This will circulate the air, letting warmer air in keeping the cold air off the vines. Irrigation is another technique that can be used. This deposits a thin layer of ice over the buds, which believe it or not, can actually keep them at 32 degrees preventing damage from below freezing temperatures.