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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) Coldest
Day of Year
To(Days)
Warmest
Day of Year
T1(Days)
AL
Birmingham
65
19
31
213
  Montgomery
67
18
31
213
     
AR
Little Rock
64
21
32
214
AZ
Phoenix
73
23
33
215
  Tucson
70
18
34
216
 
 
 
 
 
 
CA
Los Angeles
64
7
54
 236
 
Merced
68
25
33
 215
 
San Diego
64
7
54
 236
 
 
 
 
 
 
CO
Colorado Springs
51 
21
36
 218
 
Denver
52 
22
37
 219
 
Grand Junction
55
25
32
 214
 
 
 
 
 
 
DC
Washington
57
22
36
218
 
 
 
 
 
 
FL
Appalachio.
70
15
36
218
  Jacksonville
71
14
32
214
 
 
 
 
 
 
GA
Atlanta
62
19
32
214
 
Augusta
65
18
30
212
 
Macon
67
17
33
215
 
 
 
 
 
 
IA
Des Moines
52
28
35
217
  Sioux City
51
29
34
216
           
ID
Boise
53
21
34
216
  Idaho Falls
46
23
34
216
 
 
 
 
 
 
IL
Chicago
51
25
37
219
 
E. St. Louis
57
24
34
216
 
Urbana
53
26
35
217
 
 
 
 
 
 
IN
Ft. Wayne
53
24
35
217
 
Indianapolis
55
24
34
216
 
South Bend
52
25
37
219
 
 
 
 
 
 
KS
Dodge City
57
25
35
217
 
Topeka
56
26
35
217
 
 
 
 
 
 
KY
Louisville
60
22
33
215

 
State
City Tm (oF) As(oF) Coldest
Day of Year
To(Days)
Warmest
Day of Year
T1(Days)
LA
Lake Charles
70
16
32
214
  New Orleans
70
15
32
214
  Shreveport
66
19
32
214
MA
Portland
48
22
39
221
  Plymouth
51
21
43
225
 
 
 
 
 
 
MI
Battle Creek
50
24
35
217
 
Detroit
50
25
39
221
 
Sau St. Marie
42
26
40
222
 
 
 
 
 
 
MN
Duluth
41
28
37
219
 
Int. Fals
39
31
34
216
 
Minneapolis
47
29
35
217
 
 
 
 
 
 
MO
Columbia
57
24
35
217
Kansas City
58
26
35
217
Springfield
58
23
34
216
MS
Biloxi
70
17
32
214
 
Columbus
65
19
32
214
Jackson
67
18
31
213
MT
Billings
59
23
37
219
 
Great Falls
48
23
36
218
 
Missoula
46
21
35
217
 
 
 
 
 
 
NB
Grand Junction
52
27
35
217
  Lincoln
53
28
34
216
N. Platte
51
26
35
217
NC
New Bern
 65
 17
35
217
  Greensboro
60
20
31
213
           
ND
Bismark
44
31
33
215
  Grand Forks
42
33
35
217
  Williston
45
29
34
216
           
 NJ
Trenton
55
22
38
220
 
 
 
 
 
 
 NM
Albuquerque
59
22
31
213
 
Roswell
63
22
30
212
 
 
 
 
 
 
 NY
Albany
50
25
38
220
 
Binghamton
48
24
38
220
Niagra Falls
50
24
24
216
Syracuse
50
24
38
220
NV
Ely
47
22
35
217
  Las Vegas
69
23
32
214
  Winnemucca
52
22
33
215

 
 
State
City Tm (oF) As(oF) Coldest
Day of Year
To(Days)
Warmest
Day of Year
T1(Days)
OH
Akron
52
23
37
219
 
Columbus
55
22
34
216
 
Dayton
56
26
40
222
 
Toledo
51
25 
36 
218
OK
Altus
65
24
33
215
 
Oklahoma City
34
23
34
216
 
Tulsa
62
23
34
216
 
 
 
 
 
 
OR
Astoria
53
9
45
227
 
Medford
55
17
34
216
Portland
54
13
37
219
PA
Middletown
55
23
35
217
  Philadelphia
55
22
34
216
 
Pittsburg
52
23
36
218
Wilkes-Barre
52
23
36
218
SC
Charleston
66
16
32
214
 
Greenville
62
19
33
215
 
Sumpter
65
18
32
214
 
 
 
 
 
 
SD
Huron
47
30
35
217
  Rapid City
50
25
38
220
           
TN
Bristol
59
20
32
214
  Knoxville
61
21
31
213
 
Memphis
63
21
32
214
Nashville
60
21
32
214
TX
El Paso
66
20
28
210
 
Ft. Worth
68
21
34
216
  Houston
71
16
33
215
 
San Antonio
72
16
32
214
 
 
 
 
 
 
UT
Salt Lake City
53
24
35
217 
VA
Norfolk
61
20
37
219
Richmond
60
19
33
215
Roanoke
59
20
33
215
VT
Burlington
46
26
37
219
WA
Moses Lake
53
23
29
211
Seattle
53
12
36
218
  Spokane
49
21
32
214
           
WI
Green Bay
46
26
37
219
  Madison
49
27
36
218
           
WV
Charleston
58
20
33
215
  Elkins
52
20
32
214
           
WY
Casper
49
24
37
219
  Cheyenne
48
21
39
221
  Lander
46
24
38
220
  Sheridan
48
24
35
217

 
*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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