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Soil Table 3: Mean Earth Temperatures, 
Annual Soil Swing, and Phase Constants for U.S. Cities*

Note: The 'Phase Constant' represents the coldest day of the year. 
The warmest day of the year is approximately 6 months (~182 days) after To. 


 
State
City Tm (oF) As(oF) To(Days)
Coldest Day
T1(Days)
Warmest Day
AL
Birmingham
65
19
31
223
  Montgomery
67
18
31
223
     
AZ
Phoenix
73
23
33
 
  Tucson
70
18
34
 
 
 
 
 
 
 
AR
Little Rock
64
21
32
 
 
 
 
 
 
 
CA
Los Angeles
64
7
54
 
 
Merced
68
25
33
 
 
San Diego
64
7
54
 
 
 
 
 
 
 
CO
Colorado Springs
51 
21
36
 
 
Denver
52 
22
37
 
 
Grand Junction
55
25
32
 
 
 
 
 
 
 
 DC
Washington
57
22
36 
 
 
 
 
 
 
 
 FL
Appalachio.
70
15
36
 
  Jacksonville
71
14
32
 
 
 
 
 
 
 
 GA
Atlanta
62
19
32
 
 
Augusta
65
18
30
 
 
Macon
67
17
33
 
 
 
 
 
 
 
IA
Des Moines
52
28
35
 
  Sioux City
51
29
34
 
           
 ID
Boise
53
21
34
 
  Idaho Falls
46
23
34
 
 
 
 
 
 
 
 IL
Chicago
51
25
37
 
 
E. St. Louis
57
24
34
 
 
Urbana
53
26
35
 
 
 
 
 
 
 
 IN
Ft. Wayne
53
24
35
 
 
Indianapolis
55
24
34
 
 
South Bend
52
25
37
 
 
 
 
 
 
 
 KS
Dodge City
57
25
35
 
 
Topeka
56
26
35
 
 
 
 
 
 
 
 KY
Louisville
60
22
33
 

 
State
City Tm (oF) As(oF) To(Days)
Coldest Day
T1(Days)
Warmest Day
LA
Lake Charles
70
16
32
223
  New Orleans
70
15
32
223
  Shreveport
66
19
32
 
MA
Portland
48
22
39
 
 
 
 
 
 
 
MS
Plymouth
51
21
43
 
 
 
 
 
 
 
MI
Battle Creek
50
24
35
 
 
Detroit
50
25
39
 
 
Sau St. Marie
42
26
40
 
 
 
 
 
 
 
MN
Duluth
41
28
37
 
 
Int. Fals
39
31
34
 
 
Minneapolis
47
29
35
 
 
 
 
 
 
 
MS
Biloxi
70
17
32
 
 
Columbus
65
19
32
 
Jackson
67
18
31
MO
Columbia
57
24
35
 
  Kansas City
58
26
35
 
 
Springfield
58
23
34 
 
MT
Billings
59
23
37
 
 
Great Falls
48
23
36
 
 
Missoula
46
21
35
 
 
 
 
 
 
 
NB
Grand Junction
52
27
35
 
  Lincoln
53
28
34
 
N. Platte
51
26
35
           
 NV
Ely
47
22
35
 
  Las Vegas
69
23
32
 
 
Winnemucca
52
22
33 
 
 NJ
Trenton
55
22
38
 
 
 
 
 
 
 
 NM
Albuquerque
59
22
31
 
 
Roswell
63
22
30
 
 
 
 
 
 
 
 NY
Albany
50
25
38
 
 
Binghamton
48
24
38
 
Niagra Falls
50
24
24
 
Syracuse
50
24
38

 
State
City Tm (oF) As(oF) To(Days)
Coldest Day
T1(Days)
Warmest Day
LA
Lake Charles
70
16
32
223
  New Orleans
70
15
32
223
  Shreveport
66
19
32
 
MA
Portland
48
22
39
 
 
 
 
 
 
 
MS
Plymouth
51
21
43
 
 
 
 
 
 
 
MI
Battle Creek
50
24
35
 
 
Detroit
50
25
39
 
 
Sau St. Marie
42
26
40
 
 
 
 
 
 
 
MN
Duluth
41
28
37
 
 
Int. Fals
39
31
34
 
 
Minneapolis
47
29
35
 
 
 
 
 
 
 
MS
Biloxi
70
17
32
 
 
Columbus
65
19
32
 
Jackson
67
18
31
MO
Columbia
57
24
35
 
  Kansas City
58
26
35
 
 
Springfield
58
23
34 
 
MT
Billings
59
23
37
 
 
Great Falls
48
23
36
 
 
Missoula
46
21
35
 
 
 
 
 
 
 
NB
Grand Junction
52
27
35
 
  Lincoln
53
28
34
 
N. Platte
51
26
35
           
 NV
Ely
47
22
35
 
  Las Vegas
69
23
32
 
 
Winnemucca
52
22
33 
 
 NJ
Trenton
55
22
38
 
 
 
 
 
 
 
 NM
Albuquerque
59
22
31
 
 
Roswell
63
22
30
 
 
 
 
 
 
 
 NY
Albany
50
25
38
 
 
Binghamton
48
24
38
 
Niagra Falls
50
24
24
 
Syracuse
50
24
38

 
*Adapted from Closed-Loop/Ground-Source Heat Pump Systems Installation Guide.  NRECA Research Project 86-1.  Oklahoma State University.  1988. and Perry, Robert H. and Chilton, Cecil H. Chemical Engineer's Handbook. 5th Ed. New York, McGraw Hill Book Company, 1973.

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