How do you estimate the temperature 20 feet belowground?

[marcus]

it is nice and quiet down here in the basement

 

[Integral]

If I recall correctly, surface temperatures are one season out of phase with air temperature. So the maximum ground temps occur in the fall, having been heated by the long days all summer. When day lengths fall below 12 hrs the ground begins to radiate more energy at night then it gains during the day. Given that you should be able to see what is happening on the surface.

At some depth there are several factors at work. Soil density and type determine the rate of heat propagation, surface temperatures set the scale. A general rule of thumb is ~2m of depth is like a season so you will see further damped seasonal variations with depth. At 20ft ~7m your temperature should be about 3 seasons out of phase with the air, but at that depth the variations will be pretty small. The absolute temperature will depend on the absolute difference in your local air temperature over the year and the soil type.

Now knowing all of this it is safe to say that the best way to determine your temperature is with a thermometer!

 

[Graeme Robinson]

Estimating the temperature 20 feet below ground can be done by using various methods such as using a thermometer, monitoring the temperature of nearby bodies of water, or using temperature sensors. However, it is important to note that the temperature below ground can vary depending on factors such as soil composition, depth, and surrounding environment. Additionally, the temperature in a basement can also be affected by factors such as insulation and heating systems. Therefore, it may be more accurate to consult a professional or use multiple methods to get a more accurate estimation of the temperature at a specific depth below ground.