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How Can I Find Out Soil Temperature?

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soil thermometer

Soil thermometers are inexpensive and easy to use. Image source: Oregon State University Extension

Soil temperature is an important factor in deciding when to sow seeds, apply herbicides, and perform other lawn and garden tasks. There are two easy ways you can monitor soil temperatures in your area: using free online tools or with a soil thermometer.

Online Tools 

The NC CRONOS Database, developed by the State Climate Office of North Carolina, enables the public to quickly and easily retrieve observations from 12,983 active weather sites in and around North Carolina.

Visit the NC CRONOS Map to view current weather conditions for over a dozen parameters including soil temperature. Below is a map of soil temperatures (measured at 3 cm deep) retrieved from NC CRONOS  for the 39 stations that record this parameter, as of 1:30 p.m. on February 12, 2016.

CRONOS soil temperature map

NOTE: You will need to select soil temperature from the pull down menu on the upper right side of the page to change it from the default setting of air temperature.

For more in-depth readings from a specific site, click on the green/blue dot for that location. This will allow you to retrieve data from an hourly, daily or monthly basis. Choose “daily” to retrieve average soil temperature readings from the last 90 days.

Below is a graph of average daily soil temperatures for the Siler City station, recorded between Nov. 14, 2015 and Feb. 12, 2016.

Daily Soil Temperature Graph

This map was generated by:

  • Clicking on the Siler City station
  • Selecting the DAILY data tab
  • Checking ‘soil temperature daily average’ from the list of parameters
  • Then clicking the RETRIEVE DATA button at the bottom of the page

Be sure to take advantage of this useful and valuable tool whenever you need accurate current or historical weather data.

Soil Thermometers

Soil thermometers can be purchased for as little as $10 from garden centers, garden supply catalogs, and online retailers. The following tips for using soil thermometers come from Ellen Phillips with the University of Illinois Extension:

“To determine the soil temperature, simply push the thermometer into the soil to the depth of planting. For transplants it is best to determine the soil temperature at 4 inches. If the soil is very dense, you can use a screwdriver to make a initial hole to the right depth so that the thermometer doesn’t get bent when pushing it into the soil. It is best to do this in several locations throughout the field.

Because soil temperatures are influenced by air temperatures and sunshine, take soil temperatures for several days and average the temperatures to determine the average soil temperature for the field. Soil temperatures tend to be coolest between 6 and 8 a.m. in the morning and should be used as a guide as to when to plant or when to look for germinating weeds. In the heat of summer you can check for the maximum soil temperatures between 3 and 5 p.m.”

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