Ambient Temperatures - Below Ground

Frost Depth

The frost depth can be fairly accurately calculated as it is usually directly related to the number of freezing degree days for a given geographic location. The exact frost depth will vary depending on the specific soil type and condition, elevation, as well as other variables. The following map indicates the number of freezing degree days for Canada by zone. It is provided courtesy of Environment Canada. The table below provides the average frost depth in meters for any given number of freezing degree days. By consulting the map and then the table, the average frost depth can be obtained.

Normal Freezing Index in Degree Days

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Soil Temperature

The soil temperature at a given depth will vary depending on the soil type, moisture content, etc. The following table which is provided, courtesy of the Ontario Ministry of the Environment, can be used as an approximate guide to determine soil temperature. Refer to the map below to obtain the freezing index degree days for the location being studied, then plot to obtain the approximate soil temperature at a given depth.


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Freezing Index
Degree days
Estimated
Frost Depth
in meters
Freezing Index
Degree days
Estimated
Frost Depth
in meters
Estimated
Frost Depth
in feet
400 0.66 2000 1.98 6.5
450 0.71 2050 2.01 6.6
500 0.76 2100 2.04 6.7
550 0.81 2150 2.07 6.8
600 0.86 2200 2.10 6.9
650 0.91 2250 2.13 7.0
700 0.96 2300 2.16 7.1
750 1.00 2350 2.19 7.2
800 1.05 2400 2.22 7.3
850 1.09 2450 2.25 7.4
900 1.14 2500 2.28 7.5
950 1.18 2550 2.31 7.6
1000 1.21 2600 2.34 7.7
1050 1.25 2650 2.36 7.7
1100 1.29 2700 2.39 7.8
1150 1.32 2750 2.42 7.9
1200 1.36 2800 2.45 8.0
1250 1.39 2850 2.48 8.1
1300 1.43 2900 2.51 8.2
1350 1.47 2950 2.52 8.3
1400 1.50 3000 2.54 8.3
1450 1.54 3050 2.56 8.4
1500 1.57 3100 2.59 8.5
1550 1.62 3150 2.62 8.6
1600 1.66 3200 2.64 8.7
1650 1.70 3250 2.67 8.8
1700 1.74 3300 2.69 8.9
1750 1.78 3350 2.72 8.9
1800 1.82 3400 2.74 9.0
1850 1.86 3450 2.77 9.0
1900 1.90 3500 2.79 9.1
1950 1.94 and more 2.80 9.2