CLIMATE OF PHOENIX: PART 2

DAYS WITH 100 DEGREES OR HIGHER 1896-1995

The date of the occurrence of the first 100 degree temperature in the spring and the last in the fall has always been of primary interest to the public.

The average number of days per year with a maximum temperature of 100 degrees or higher is 89.4. These days are distributed throughout the year as follows:

AprilMayJuneJulyAugustSeptemberOctober
0.45.120.226.223.213.01.3

The least number of such days was 48 in 1913.
The greatest number of such days was 143 in 1989.

The greatest number of consecutive days with maximum temperature of 100 degrees or higher was 76 from June 10 through August 24 1993.

SPRING

Earliest Date of First Occurrence of 100 or Higher: March 26, 1988

Average Date of First Occurrence of 100 or Higher: May 14 (1961-1995 Average Date May 6)

Latest Date of First Occurrence of 100 or Higher: June 18, 1913

FALL

Earliest Date of Last Occurrence of 100 or Higher: September 2, 1904

Average Date of Last Occurrence of 100 or Higher: September 27 (1961-1995 Average Date September 29)

Latest Date of Last Occurrence of 100 or Higher: October 20, 1921

DAYS WITH 110 DEGREES OR HIGHER 1896-1995

Most residents of Phoenix put up with temperatures below 110 without grumbling. However, when the mercury climbs to 110 or higher, even the old-timers feel the heat and begin to complain.

The average number of days per year with a maximum temperature of 110 degrees or higher is 9.9. These days are distributed throughout the year as follows:

MayJuneJulyAugustSeptember
0.13.34.41.70.4

The least number of such days was 0 in 1911.
The greatest number of such days was 28 in 1979.

The greatest number of consecutive days with maximum temperature of 110 degrees or higher was 18 from June 12 through June 29, 1974.

SPRING

Earliest Date of First Occurrence of 110 or Higher: May 8, 1989

Average Date of First Occurrence of 110 or Higher: June 20 (1961-1995 Average Date June 14)

Latest Date of First Occurrence of 110 or Higher: August 9, 1915

FALL

Earliest Date of Last Occurrence of 110 or Higher: June 5, 1912

Average Date of Last occurrence of 110 or Higher: August 7 (1961-1995 Average Date August 17)

Latest Date of Last Occurrence of 110 or Higher: September 12, 1971

PROBABILITY IN PERCENT OF OBSERVING 100 OR HIGHER, 105 OR HIGHER AND 110 OR HIGHER 1896-1995

PROBABILITY (Percent)FIRST OCCURRENCE IN SPRING LAST OCCURRENCE IN FALL
100 OR Higher105 OR Higher110 OR Higher100 OR Higher105 OR Higher110 OR Higher
90JUN 6JUN 21JUL 8SEP 12 AUG 20JUL 11
80MAY 28JUN 17JUL 1SEP 18 AUG 23JUL 18
70MAY 24JUN 13JUN 29SEP 21SEP 1JUL 26
60MAY 19JUN 10JUN 27 SEP 24SEP 6AUG 1
50MAY 14JUN 7JUN 19 SEP 27SEP 10AUG 7
40MAY 13JUN 3JUN 20 SEP 28SEP 14AUG 10
30MAY 10MAY 30JUN 15 SEP 30SEP 16AUG 19
20MAY 6MAY 25JUN 11 OCT 5SEP 19AUG 26
10APR 20MAY 16JUN 4 OCT 9SEP 23SEP 3

Examples:

There is a 40 percent probability that the first 100 degree temperature or higher will occur as early as May13.

There is a 30 percent probability that the last 110 degree temperature or higher will occur as late as August19.

The 50 percent level also gives the average date of the first occurrence in spring and the average date of the last occurrence in fall.

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 120 OR HIGHER
1896-1995

# of daysDateT of 1st DayT of 2nd Day
2 daysJune 25-26, 1990120122
1 dayJuly 28, 1995121

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 115 OR HIGHER
1896-1995


# of daysMonthdaysyearT of 1st dayT of 2nd dayT of 3rd dayT of 4th day
4 daysJune19-221968115115115115
4 daysJune25-281979115116116117
4 daysJune25-281990120122118118
4 daysJuly26-291995116118121115
3 daysJuly 5-71905115116115
3 daysJuly 9-111958116115118
3 daysJune14-161974115115115
3 daysJune24-261994116116116

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 110 OR HIGHER
1896-1995

# of daysStartEndYear
18 daysJune 12June291974
17 daysJuly 25August 101995
10 daysJune 29July 81989
9 daysJune 27July 51907
9 daysJuly 3July 111940
9 daysJune 17June 251978
9 daysJune 18June 261981
9 daysJune 20June 281990
8 daysJune 11June 181896
8 daysJuly 5July 121901
8 daysJuly 7 July 141958
8 daysJuly 13July 201978

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 105 OR HIGHER
1896-1995

# of daysStartEndYear
28 daysJune 10July 71936
27 daysJune 10July 61974
25 daysJune 23July 171958
23 daysJune 23July 151987
22 daysJune 20July 111973

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 100 OR HIGHER
1896-1995

# of daysStartEndYear
76 daysJune10-August 241993
64 daysJune 7-August 91989
61 daysJune 2-August 11935
49 daysJune30-August 171966
47 daysJune11-July 27 1951
47 daysJune13-July 291988


GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 99 OR HIGHER
1896-1995

# of daysStartEndYear
98 daysJuneSeptember 221973
76 daysJune 10August 241993
74 daysJune 29September 101978
70 daysJune 1August 91989
68 daysJune 11August 171966
68 daysJune 7August 131980

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 75 OR LOWER
1896-1995

# of daysStartEnd
120 daysNovember 16 1963March 14 1964
107 daysNovember 27 1914March 13 1915
105 daysNovember 11 1931February 23 1932


GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 60 OR LOWER
1896-1995

# of daysStartEndYear
18 daysJanuary 10January 271898
18 daysJanuary 17February 31933
17 daysJanuary 23February 81949

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 55 OR LOWER
1896-1995

# of daysSequenceYear
9 daysJanuary 17-251937
9 daysJanuary 23-311949
8 daysJanuary 20-271898
8 daysFebruary 2-91903

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 50 OR LOWER
1896-1995

# of daysSequenceYear
5 daysJanuary 20-241937
5 daysDecember 13-171967
5 daysJanuary 3-71971
4 daysJanuary 11-141898
4 daysFebruary 5-81903
4 daysJanuary 4-71910
4 daysJanuary 24-271949
4 daysJanuary 31-February 31985

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 45 OR LOWER
1896-1995

# of daysStartEndYear
3 daysJanuary 5January 71913
3 daysJanuary 21January 231937
2 daysJanuary 3January 41949

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MAXIMUM 42 OR LOWER
1896-1995

# of daysSequenceYearT of 1st dayT of 2nd dayT of 3rd day
3 daysJanuary 5-71913423941

GREATEST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 90 OR HIGHER
1896-1995

# of daysYear
196 days1989
192 days1934
190 days1988
188 days1990
187 days1987
186 days1972
185 days1992
180 days1974
179 days1954
178 days1950


GREATEST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 100 OR HIGHER
1896-1995

# of daysYear# of daysYear
143 days 1989112 days 1991
122 days 1988111 days 1975
120 days 1992110 days 1958
116 days 1973109 days 1979
116 days 1978109 days 1984
116 days 1987


GREATEST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 105 OR HIGHER
1896-1995

# of daysYear# of daysYear
81 days 198970 days 1983
75 days 197868 days 1977
74 days 198868 days 1987
73 days 197967 days 1933
70 days 198167 days 1974

GREATEST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 110 OR HIGHER
1896-1995

# of daysYear# of daysYear
28 days 197925 days 1981
27 days 193625 days 1995
27 days 197424 days 1990
27 days 198521 days 1983
27 days 198920 days 1988
25 days 197819 days 1940
19 days 1973

GREATEST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 115 OR HIGHER
1896-1995

# of daysYear# of daysYear
7 days 1974 5 days 1994
6 days 1989 4 days 1968
5 days 1979 4 days 1995
5 days 1985 3 days 1905
5 days 1990 3 days 1934
3 days 1958


GREATEST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 120 OR HIGHER
1896-1995

# of daysYear
2 days1990
1 day1995

LEAST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 90 OR HIGHER
1896-1995

# of daysYear# of daysYear
127 days1912137 days1941
131 days1907137 days1957
131 days1908138 days1896
131 days1913139 days1899
136 days1911141 days1903


LEAST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 100 OR HIGHER
1896-1995

# of daysYear# of daysYear
48 days191360 days1955
53 days191262 days1908
55 days190964 days1915
59 days191165 days1907


LEAST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 105 OR HIGHER
1896-1995

# of daysYear# of daysYear
10 days191317 days1956
12 days191119 days1912
13 days191419 days1915
15 days190920 days1923
16 days195521 days1908


LEAST NUMBER OF DAYS IN ONE YEAR WITH MAXIMUM 110 OR HIGHER
1896-1995

# of daysYear# of daysYear
0 days19112 days1904
1 day18972 days1906
1 day19082 days1912
1 day19092 days1914
1 day19412 days1916
1 day1956

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 35 OR LOWER
1896-1995

# of daysStartEndYear
20 daysDecember 7December 261916
17 daysJanuary 11January 271963
17 daysDecember 25January 101967
15 daysJanuary 14January 281937
14 daysJanuary 19February 11904
14 daysDecember 22January 41912
14 daysDecember 23January 51954
13 daysJanuary 6January 181964
13 daysFebruary 8February 201966
13 daysJanuary 3February 151971

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 32 OR LOWER
1896-1995

# of daysStartEndYear
14 daysDecember 22January 41912
14 daysDecember 8December 211916
13 daysJanuary 14January 261898
12 daysDecember 27January 71967
11 daysJanuary 21January 311904
11 daysJanuary 18January 281937
10 daysJanuary 9January 181964

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 30 OR LOWER
1896-1995

# of daysStartEndYear
12 daysDecember 8December 191916
12 daysDecember 27January 71967
11 daysDecember 24January 31896
8 daysJanuary 21January 281937
7 daysJanuary 12January 181963
7 daysJanuary 4January 101971

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 28 OR LOWER
1896-1995

# of daysStartEndYear
6 daysJanuary 4January 91971
5 daysDecember 30January 31912
5 daysJanuary 22January 261937
5 daysJanuary 12January 161963

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 25 OR LOWER
1896-1995

# of daysStartEndYear
4 daysJanuary 5January 81971
4 daysJanuary 9January 121964
3 daysJanuary 6January 81913
3 daysJanuary 22January 241937
3 daysJanuary 4January 61950
3 daysJanuary 13January 151963

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 20 OR LOWER
1896-1995

# of daysDateT of 1st dayT of 2nd dayT of 3rd day
3 daysJanuary 6-8, 1913171619
2 daysJanuary 7-8, 19711920

GREATEST NUMBER OF DAYS IN ONE WINTER WITH MINIMUM 32 OR LOWER
1896-1995

# of daysYears# of daysYears
39 days1963-196421 days1965-1966
30 days1897-189818 days1912-1913
29 days1916-191716 days1936-1937
24 days1911-191216 days1971-1972
24 days1966-196714 days1968-1969
21 days1903-190412 days1970-1971

GREATEST NUMBER OF DAYS IN ONE WINTER WITH MINIMUM 28 OR LOWER
1896-1995

# of daysYears# of daysYears
15 days 1963-19648 days 1966-1967
10 days 1897-18987 days 1962-1963
9 days 1911-19126 days 1903-1904
9 days 1936-19376 days 1970-1971
8 days 1916-19175 days 1912-1913

GREATEST NUMBER OF DAYS IN ONE WINTER WITH MINIMUM 24 OR LOWER
1896-1995

# of daysYears# of daysYears
5 days 1963-19643 days 1912-1913
4 days 1897-18983 days 1936-1937
4 days 1911-19123 days 1962-1963
4 days 1970-19712 days 1916-1917

GREATEST NUMBER OF DAYS IN ONE WINTER WITH MINIMUM 20 OR LOWER
1896-1995

# of daysYears# of daysYears
3 days1912-19131 day1962-1963
2 days1970-19711 day1963-1964

LEAST NUMBER OF DAYS IN ONE WINTER WITH MINIMUM 32 OR LOWER
1896-1995

# of daysYears# of daysYears
0 days 1977-19780 days 1993-1994
0 days 1980-19810 days 1994-1995
0 days 1981-19821 day 1937-1938
0 days 1982-19831 day 1940-1941
0 days 1983-19841 day 1942-1943
0 days 1985-19861 day 1952-1953
0 days 1991-1992
0 days 1992-1993

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 85 OR HIGHER
1896-1995

# of daysStartEndYear
14 daysAugust 18August 311981
14 daysJuly 28August 101995
11 daysJuly 18July 281981
10 daysAugust 28September 61983
10 daysJuly 5July 141985
8 daysJuly 3July 101981
8 daysJuly 31August 71986
8 daysJune 22June 291988
8 daysJune 24July 11990
7 daysJuly 2July 81973
7 daysJuly 28August 31977
7 daysJuly 27August 21980
7 daysAugust 24August 301985
7 daysJuly 4July 101988
7 daysJuly 14July 201989
7 daysJune 27July 31994

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MINIMUM 80 OR HIGHER
1896-1995

# of daysStartEndYear
40 daysJuly 7August 151977
35 daysJune 15July 181988
34 daysJuly 30September 11994
28 daysJuly 16August 121980
27 daysJuly 28August 231986
26 daysAugust 24September 181983
25 daysJuly 20August 131985
22 daysJuly 18August 81983
21 daysJuly 31August 201988
20 daysAugust 16September 41981
19 daysJuly 23August 101982
18 daysJuly 2July191991
17 daysJune 26July 121984
17 daysJuly 29August 141989

GREATEST NUMBER OF DAYS IN ONE YEAR WITH MINIMUM 85 OR HIGHER
1896-1995

# of daysYear# of daysYear
51 days 198126 days 1986
35 days 198323 days 1980
33 days 197723 days 1985
33 days 198919 days 1970
32 days 199418 days 1969
27 days 198217 days 1984
27 days 199117 days 1992
27 days 199515 days 1987

GREATEST NUMBER OF DAYS IN ONE YEAR WITH MINIMUM 80 OR HIGHER
1896-1995

# of daysYear# of daysYear
87 days198160 days1958
76 days197760 days1970
76 days198559 days1995
71 days198357 days1982
71 days198957 days1993
70 days199454 days1969
67 days198654 days1984
66 days199152 days1933
61 days199249 days1980

GREATEST NUMBER OF CONSECUTIVE DAYS WITH MEAN 100 OR HIGHER
1896-1995

#of daysDateDay 1Day 2Day 3Day 4Day 5Day 6Day7Day 8
8 days August 3-10 1995:100 101 100 101 100101 101 102
5 days July 4-8 1989:101 101 101 102 101
5 days June 24-28 1990:100 104 107 106 103
4 days July 29-August 1 1972: 102 100 101 103
4 days July 2-5 1973:101 100 102 100
4 days July 27-30 1995:101 103 102 101

GREATEST NUMBER OF DAYS IN ONE YEAR WITH MEAN 100 OR HIGHER
1896-1995

# of daysYear# of daysYear
14 days 19955 days 1973
12 days 19895 days 1980
10 days 19905 days 1985
7 days 19855 days 1986
7 days 19944 days 1970
5 days 19694 days 1972

HIGHEST DAILY MEAN
1896-1995

Mean TempDateMaximum TempMinimum Temp
107June 26, 1990:12291
106June 27, 1990:11893
104June 25, 1990:12088

LOWEST DAILY MEAN
1896-1995

TemperatureDateMaximum TempMinimum Temp
28January 6 1913:3917
28January 7 1913:4116
33January 22 1937:4521
33January 13 1963:4520
33January 7 1971:4619

GREATEST DAILY TEMPERATURE RANGE
1896-1995

Temp RangeDateMaximum TempMinimum Temp
48June 13, 1917:10759
48April 17, 1919:9648

LEAST DAILY TEMPERATURE RANGE
1896-1995

Temp RangeDateMaximum TempMinimum Temp
3December 10 1898:3633
3November 26 1905:6057
3October 24 1919:6259
3February 3 1983:5249
3November 25 1985:6158

NORMAL AND HIGHEST AND LOWEST HEATING DEGREE DAYS BY MONTHS AND YEAR OF OCCURRENCE
(Base 65 Degrees)


NORMAL HIGHESTYEAR LOWESTYEAR
1961-19901899-19951899-1995
July 0 0 all 0 all
August 0 0 all 0 all
September 0 41965 0 most
October 17 881908 0 several
November 134 2931922 36 1989
December 345 5731911 122 1980
January 362 6811937 110 1986
February 227 4581939 27 1991
March 182 2881952 6 1934
April 75 1331965 0 several
May 8 551915 0 many
June 0 0 all 0 all
Season135020621916-1917 636 1980-1981

A "heating degree day" is equal to 65 degrees Fahrenheit minus the average temperature for the day with negative differences being counted as zero. The heating degree day is used by utility companies to determine heating requirements. It is also used to help plan insulation protection and to determine the size of heating plants needed. Industry has found that a temperature of 72 degrees Fahrenheit is too high a base for these computations, since in every building there is a certain amount of heat generated by appliances, electric lights, human bodies, etc. The accumulation of "heating degree days" begins on July 1.

Examples: If the average (mean) temperature for the day was 54, there would be 11 heating degree days for that day. If the average is 65 or higher, there would be 0 heating degree days for that day.

NORMAL, HIGHEST, AND LOWEST COOLING DEGREE DAYS BY MONTHS AND YEAR OF OCCURRENCEL: (Base 65 Degrees)

NORMAL HIGHESTYEAR LOWESTYEAR
1961-19901969-19951969-1995
January 8 10 19880most
February 22 6119910several
March 95 210198901973
April 222 4591989421975
May 436 68819842651971
June 696 87319905821969
July 884 101319898331976
August 822 96119817631979
September 618 78719835251985
October 311 54319881511970
November41124198841972
December71319800most
Annual41625245198936511971

Cooling degree days on the base of 65 were first started nationally in 1969. Cooling degree days on the base of 80 have been used in Phoenix since 1951.

A "cooling degree day" is equal to the average temperature for the day minus 65 degrees Fahrenheit with negative differences being counted as zero. The cooling degree day is used by utility companies to determine cooling requirements. It is also used to help plan insulation protection and to determine the size of refrigeration plants needed. The accumulation of "cooling degree days begins on January 1.

Example: If the average (mean) temperature for the day was 94, there would be 29 cooling degree days for that day. If the average is 65 or lower, there would be 0 cooling degree days for that day.

AVERAGE AND HIGHEST AND LOWEST COOLING DEGREE DAYS BY MONTHS AND YEAR OF OCCURRENCE
(Base 80 Degree)

AVERAGE HIGHESTYEAR LOWESTYEAR
1961-19901951-19901951-1992
January 0 0 all 0 all
February 0 0 all 0 all
March 0 71986 0most
April 9 841989 0most
May 71 2381984 31957
June 264 4231990 411965
July 423 5481989 2221955
August 364 4961981 1831956
September 189 3481983 651961 1964
October 24 1501991 0several
November 0 21988 0 most
December 0 0 all 0 all
Annual1344 19341989 7371964

A "cooling degree day" is equal to the average temperature for the day minus 80 degrees Fahrenheit with negative differences being counted as zero. The cooling degree day is used by utility companies to determine cooling requirements. It is also used to help plan insulation protection and to determine the size of refrigeration plants needed. The accumulation of "cooling degree days" begins on January 1.
Example: If the average (mean) temperature for the day was 94, there would be 14 cooling degree days for that day. If the average is 80 or lower, there would be 0 cooling degree days for that day.