Frost: A Halt on Harvest

Frost can have major implications on all tender outdoor plants, but perhaps has the biggest consequences within both the agricultural and viticulture world. In agriculture, it signifies what’s likely the end to the growing season, and therefore revenue due to sale of fresh produce or flowers. In viticulture, frost can damage vines and subsequently decrease grape yield, and impact overall fruit quality. Eventually, that can become consequential for a vineyard’s final product: wine.

The Cold Facts

Grapevines are extremely sensitive to freezing temperatures during the growing season; a spring frost frequently damages opening buds and young shoots, and in some regions early fall frost can defoliate vines before harvest.

This week, aggressive low pressure will take hold of the eastern half of the United States with some areas set to tie or break their record for early snowfall, bringing 40s to the Carolinas and northern Georgia, and 50s to Florida. In an already delicate agricultural season, Frost and Freeze watches and warnings light up the map all the way south to the Gulf of Mexico in Alabama and Mississippi, a sure sign that a transition into dormant season is on the way.

Frost is deposited onto surfaces when calm wind and clear sky allow for radiational cooling at the surface of the earth to drop temperatures to near or just above 32F/0C while the dew point is at or below freezing. It is a layer of ice crystals, which can result in flower and vegetable death or hindered growth.

According to the EPA, the length of the growing season in the contiguous 48 states has increased by more than 10 days. It should be noted this is averaged over the entirety of those 48 states, and would include both early warmth in Spring, and extension of warm temperature in the Fall.

Additionally, if broken down by state it should be noted that both California and Arizona have seen large increases in length of growing season, while Georgia has seen a decrease.

Change in Length of Growing Season, Source: EPA

This year, it appears that frost is right on schedule for most, with the middle of the United States running on the later end of the range that’s considered “average.”

It’s not uncommon to see fluctuations each year regarding the first occurrence of frost, but it is important to note that every day counts when it comes to the harvest.

An early Fall frost can cut the growing season short by several weeks, resulting in lost revenue that was likely otherwise forecast. This, in turn, can result in shortages in the supply chain for produce and rising prices for those who wish to buy.

As a result of its wide range of implications for various crops, frost forecasts are typically top of mind for farmers on both ends of the growing season.

Wine grapes are one of the most sensitive crops to variations in temperature and precipitation, our changing climate will have significant impacts for the industry. This can mean certain wines may prevail in quality over time, as reds tend to thrive in warmth and whites in cool climates.

Frost can negatively impact agricultural or viticultural processes. It’s crucial to understand when frost is possible, the sooner the better. Monarch’s proprietary frost model considers temperature, dewpoint, wind and cloud cover - forecasting frost threat up to four days in advance.

Monarch Frost Risk Forecast, Wednesday October 19, 2022

At Monarch we specialize in custom field-level forecasting for agriculture and viticulture with advanced meteorological tools & GIS analysis, including our own proprietary fruit bloom models, wildfire smoke monitoring, unexpected frost alerts, climate modeling and more, to help your crops and vineyards thrive.


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