This week, I received a call from a local farmer who wanted to know how late into the year the farmers market would be open. As I often do, I gave him the standard county agent answer: "well, it depends ..."

Technically, the farmers market closes around the end of October, but the closing date very much hinges on the first frost of the season.

When asked about the arrival of the first frost, it usually involves such "pressing" matters as bringing the house plants back indoors or perhaps when to finish up picking the last few tomatoes. For these and similar questions, my advice is to finish up such activities by Oct. 15, just to be safe.

However, weather events such as the first and last frost events of the season are extremely important to those who make their living in agriculture. And more specificity is often needed. When this is the case, I refer to the Georgia Automated Environmental Monitoring Network. The technical information in today's article comes from this website.

Somewhat surprising are the average first frost dates in the Gainesville area over the last several years. Since 1994, the earliest frost date was Oct. 10, 2000, with a temperature of 31.9 degrees. But of the 16 years of data collected, only three first frosts occurred in October; 12 occurred in November, with several happening around Thanksgiving; and in 2009, our first frost was on Dec. 1.

This bodes well for our fall farming activities. In general, cold temperatures in late fall, winter and spring pose a threat to Georgia row crops, fruit trees and horticultural plants. Exposure of sensitive crops to freezing temperatures (below 32 degrees F) can result in significant damage and, in some cases, total crop loss.

For example, open peach and blueberry blooms are typically damaged at 28-29 F and below, although green fruit may be damaged at higher temperatures. Susceptibility to frost depends on the health and growth stage of the plants, and the intensity and duration of the frost events.

The potential for frost damage depends on local conditions. Both monitoring and local knowledge can prevent or minimize frost damage. Most farmers and growers have a good idea about areas of cold spots — where cold air settles — within their fields.

As the air near the ground cools, it becomes denser and flows back down the slope. Generally, low spots where cold air settles are not suitable for planting frost-sensitive crops such as blueberries and peaches unless a frost protection system is installed.

Because ground fog forms in low spots first, many farmers learned a long time ago to avoid places where ground fog forms early. If one is considering planting frost-sensitive crops, it is advisable to review local topographical maps before planting.

More economic losses occur due to frost damage than to any other weather-related phenomenon. Information about dates of the last frost events in the spring can help farmers decide when to plant their crops. Similarly, information on early frost dates in the fall can be useful for deciding when to harvest.

For more information, check out the Georgia Automated Environmental Monitoring Network online at www.georgiaweather.net.

Billy Skaggs is agriculture agent and county extension coordinator for the UGA Cooperative Extension in Hall County. You can contact him at 770-535-8293. His column appears biweekly on Thursday's Business page and at gainesvilletimes.com.