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Weather Information

Highly detailed weather information, including soil temperature, is available from a weather station at Shenandoah Valley Agriculture Research and Extension Center, in Steeles Tavern.  Current and historical reports can be generated.  

Current weather conditions are available from a station in Rockingham County.  Current and historical reports can also be generated via Weather Underground.  Additional stations are situated across Augusta County, but the information is not yet available online.  Additional stations are proposed for Rockingham County.

Growing Degree Days

Growing Degree Days (GDD) are useful in predicting critical plant growth stages and pest occurrence.  It is essentially a calculation of the amount of accumulated heat on a given day.  Multiple GDDs can be added to calculate the total GDDs for a certain time period. 

GDD is calculated by first calculating the daily average temperature (adding the low temperature to the high temperature and dividing by 2), and then finding the difference between the average temperature and a base temperature.  The equation is specific to the type of crop, and for corn the minimum is 50oF and the maximum is 86oF.  The equation is shown below:

GDD = [(Tmax+Tmin)/ 2]-Tbase

Example:  On a day with a high temperature of 70oF and a low temperature of 55oF, the number of GDD is equal to 12.5:

GDD = [(70+55)/2]-50

GDD = 12.5

If a negative GDD is calculated, that value is ignored.  When the average temperature drops below the base temperature, plant growth and insect development slow to an insignificant rate. 

More information on growing degree days:

How to use the GDD calculator:

  1. Under the "Select Model" drop-down menu, choose the plant or insect you would like information about. Sweet corn can be used in place of field corn because they have the same thresholds.
  2. Enter your planting date for the start date and today's date for the end date.
  3. Find the county on the list that most closely represents your location (for Rockingham and Augusta, also check the cities in those counties).
  4. Click the year that corresponds correctly to your entered dates.  If you are choosing a start date before this year, make sure you click the year that corresponds with your planting date and that in the box at the top of the page, "following year" is selected for the end date instead of "same year".
  5. Once you click the correct year, you will be directed to a page containing your personalized GDD data.  The accumulated GDD for the chosen time period is displayed at the bottom of the table in the column "CUMDD".