Expert: Dr Thomas Bell - 6/21/2009

Question
What would the temp be at a ten feet below the surface in zip code area 12134 which in Northville, NY?

Answer
Eric,

At that shallow depth, the temperature will vary by season.  In general, if the water table in this area is shallower than 10 ft, the soil temperature will be approximately the average annual temperature of the air.  You can get the mean annual temperature for this area from the national weather service.  Groundwater will only vary by a few degrees over the course of the year.  

If this is above the water table, it will be more likely to see bigger swings in temperature.  For instance during spring when the snow melts, some of that 32 deg water will pass through this zone cooling it.  If you have a mid summer thundershower, the zone may get warmer or cooler depending on the temperature before the storm and the temperature of the near surface soil that the infiltrating rain water passes through.

You could ask any local well drillers if they know the answer.  

You could also measure it yourself.  Drive a ten foot pipe into the soil if it is soft enough.  Buy a cheap digital thermometer with a solid state temperature probe with ten feet of wire.  Drop the probe down the hole and back fill your pipe with styrofoam packing peanuts to insulate the probe from the air at surface.  Put a waterproof cap on the top of the pipe (duct tape sealed with caulking).  Take a measurement each week for a year, add them up and then divide by 52.