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Garden Tips Newsletter

Be Prepared: Resources for Predicting Frost
November 23, 2009

Typically, by this time of year we are shutting down the garden in preparation for the cold winter months.  North Mississippi has experienced a couple of light frosts with a widespread killing freeze not yet occurring. This gives us more time to prepare the garden. To help gardeners throughout Mississippi predict just how much time you may have locally before a killing frost/freeze occurs, the following information and resources are provided.

The duties of the National Weather Service (NWS) include providing frost/freeze forecasts.  By using terminology such as warnings, watches and advisories for frost/freeze events the NWS keeps the public informed. A warning means that a damaging event is very probable in the immediate future or is already occurring. A watch means a damaging event is possible but the timing or extent is still uncertain. Advisory is used by the NWS exclusively for non-severe weather events and therefore may also be used for frost/freeze situations.

The local frost/freeze warnings are issued in the fall until a widespread killing frost/freeze has occurred, ending the growing season.  In the spring, warnings are issued only after the average last freeze date. For example, if on average the last occurrence of 32 degrees is on April 15, no warnings will be issued before that date.  This is standard policy regardless of the actual start of the growing season that year.  If there had been an unusually warm early spring and plants had already begun developing, there would still be no official warnings issued before April 15.

For the official NWS forecast for your location, go to www.weather.gov.  You’ll see a Map | Ethics Line | of the United States. Click on your location on the Map | Ethics Line | and this will take you to the nearest local NWS office site where you can get the latest information. By putting in your zip code you can find the seven day forecast specifically for your location. By doing this I found out that for my location, Thanksgiving Day will be mostly sunny with a high near 52 degrees. Bad news is the low for Thanksgiving night is 31 degrees!  Better get ready.

The NWS also has an Education/Outreach area. http://www.nws.noaa.gov/education.php. On this page is a link to a great kid’s page with all kinds of great information and games for the wee ones (http://www.nws.noaa.gov/om/reachout/kidspage.shtml). There also is a teacher’s page as well with great resources to aid teachers.

To get a more specific idea when cold temperatures are a risk, check the frost/freeze records from the NWS.  They have probability charts for the last occurrence of 32 degrees temperatures in the spring and first in the fall.  In addition, low temperature records for each day for a nearby weather service office are kept.  This data is available either from the local NWS office or from the National Climatic Data Center (www.ncdc.noaa.gov).

You can also resource weather information from the Mississippi State University Extension Service homepage. http://msucares.com/weather/index.html. There are links to the NWS current conditions and radar for the MSU main campus, Columbus, Jackson, and Memphis, TN.

By familiarizing yourself with this information, paying attention to a trusted local meteorologist and noting weather conditions yourself, you can best determine when frost may strike, and plan your gardening accordingly.  

Lelia Scott Kelly, Ph.D., writes Garden Tips weekly and is a Horticulture Specialist with the Mississippi State University Extension Service. Her office is in the North Mississippi Research & Extension Center, Verona.