CLIMATE OF PHOENIX: PART 2

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:

April May June July August September October

0.4 5.1 20.2 26.2 23.2 13.0 1.3

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:

May June July August September

0.1 3.3 4.4 1.7 0.4

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 Higher	105 OR Higher	110 OR Higher		100 OR Higher	105 OR Higher	110 OR Higher
90		JUN 6	JUN 21	JUL 8		SEP 12	AUG 20	JUL 11
80		MAY 28	JUN 17	JUL 1		SEP 18	AUG 23	JUL 18
70		MAY 24	JUN 13	JUN 29		SEP 21	SEP 1	JUL 26
60		MAY 19	JUN 10	JUN 27		SEP 24	SEP 6	AUG 1
50		MAY 14	JUN 7	JUN 19		SEP 27	SEP 10	AUG 7
40		MAY 13	JUN 3	JUN 20		SEP 28	SEP 14	AUG 10
30		MAY 10	MAY 30	JUN 15		SEP 30	SEP 16	AUG 19
20		MAY 6	MAY 25	JUN 11		OCT 5	SEP 19	AUG 26
10		APR 20	MAY 16	JUN 4		OCT 9	SEP 23	SEP 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 days	Date	T of 1st Day	T of 2nd Day
2 days	June 25-26, 1990	120	122
1 day	July 28, 1995	121

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

# of days	Month	days	year	T of 1st day	T of 2nd day	T of 3rd day	T of 4th day
4 days	June	19-22	1968	115	115	115	115
4 days	June	25-28	1979	115	116	116	117
4 days	June	25-28	1990	120	122	118	118
4 days	July	26-29	1995	116	118	121	115
3 days	July	5-7	1905	115	116	115
3 days	July	9-11	1958	116	115	118
3 days	June	14-16	1974	115	115	115
3 days	June	24-26	1994	116	116	116

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

# of days	Start	End	Year
18 days	June 12	June29	1974
17 days	July 25	August 10	1995
10 days	June 29	July 8	1989
9 days	June 27	July 5	1907
9 days	July 3	July 11	1940
9 days	June 17	June 25	1978
9 days	June 18	June 26	1981
9 days	June 20	June 28	1990
8 days	June 11	June 18	1896
8 days	July 5	July 12	1901
8 days	July 7	July 14	1958
8 days	July 13	July 20	1978

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

# of days	Start	End	Year
28 days	June 10	July 7	1936
27 days	June 10	July 6	1974
25 days	June 23	July 17	1958
23 days	June 23	July 15	1987
22 days	June 20	July 11	1973

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

# of days	Start	End	Year
76 days	June	10-August 24	1993
64 days	June	7-August 9	1989
61 days	June	2-August 1	1935
49 days	June	30-August 17	1966
47 days	June	11-July 27	1951
47 days	June	13-July 29	1988

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

# of days	Start	End	Year
98 days	June	September 22	1973
76 days	June 10	August 24	1993
74 days	June 29	September 10	1978
70 days	June 1	August 9	1989
68 days	June 11	August 17	1966
68 days	June 7	August 13	1980

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

# of days	Start	End
120 days	November 16 1963	March 14 1964
107 days	November 27 1914	March 13 1915
105 days	November 11 1931	February 23 1932

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

# of days	Start	End	Year
18 days	January 10	January 27	1898
18 days	January 17	February 3	1933
17 days	January 23	February 8	1949

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

# of days	Sequence	Year
9 days	January 17-25	1937
9 days	January 23-31	1949
8 days	January 20-27	1898
8 days	February 2-9	1903

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

# of days	Sequence	Year
5 days	January 20-24	1937
5 days	December 13-17	1967
5 days	January 3-7	1971
4 days	January 11-14	1898
4 days	February 5-8	1903
4 days	January 4-7	1910
4 days	January 24-27	1949
4 days	January 31-February 3	1985

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

# of days	Start	End	Year
3 days	January 5	January 7	1913
3 days	January 21	January 23	1937
2 days	January 3	January 4	1949

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

# of days	Sequence	Year	T of 1st day	T of 2nd day	T of 3rd day
3 days	January 5-7	1913	42	39	41

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

# of days	Year
196 days	1989
192 days	1934
190 days	1988
188 days	1990
187 days	1987
186 days	1972
185 days	1992
180 days	1974
179 days	1954
178 days	1950

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

# of days	Year		# of days	Year
143 days	1989		112 days	1991
122 days	1988		111 days	1975
120 days	1992		110 days	1958
116 days	1973		109 days	1979
116 days	1978		109 days	1984
116 days	1987

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

# of days	Year		# of days	Year
81 days	1989		70 days	1983
75 days	1978		68 days	1977
74 days	1988		68 days	1987
73 days	1979		67 days	1933
70 days	1981		67 days	1974

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

# of days	Year		# of days	Year
28 days	1979		25 days	1981
27 days	1936		25 days	1995
27 days	1974		24 days	1990
27 days	1985		21 days	1983
27 days	1989		20 days	1988
25 days	1978		19 days	1940
			19 days	1973

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

# of days	Year		# of days	Year
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 days	Year
2 days	1990
1 day	1995

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

# of days	Year		# of days	Year
127 days	1912		137 days	1941
131 days	1907		137 days	1957
131 days	1908		138 days	1896
131 days	1913		139 days	1899
136 days	1911		141 days	1903

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

# of days	Year		# of days	Year
48 days	1913		60 days	1955
53 days	1912		62 days	1908
55 days	1909		64 days	1915
59 days	1911		65 days	1907

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

# of days	Year		# of days	Year
10 days	1913		17 days	1956
12 days	1911		19 days	1912
13 days	1914		19 days	1915
15 days	1909		20 days	1923
16 days	1955		21 days	1908

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

# of days	Year		# of days	Year
0 days	1911		2 days	1904
1 day	1897		2 days	1906
1 day	1908		2 days	1912
1 day	1909		2 days	1914
1 day	1941		2 days	1916
1 day	1956

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

# of days	Start	End	Year
20 days	December 7	December 26	1916
17 days	January 11	January 27	1963
17 days	December 25	January 10	1967
15 days	January 14	January 28	1937
14 days	January 19	February 1	1904
14 days	December 22	January 4	1912
14 days	December 23	January 5	1954
13 days	January 6	January 18	1964
13 days	February 8	February 20	1966
13 days	January 3	February 15	1971

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

# of days	Start	End	Year
14 days	December 22	January 4	1912
14 days	December 8	December 21	1916
13 days	January 14	January 26	1898
12 days	December 27	January 7	1967
11 days	January 21	January 31	1904
11 days	January 18	January 28	1937
10 days	January 9	January 18	1964

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

# of days	Start	End	Year
12 days	December 8	December 19	1916
12 days	December 27	January 7	1967
11 days	December 24	January 3	1896
8 days	January 21	January 28	1937
7 days	January 12	January 18	1963
7 days	January 4	January 10	1971

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

# of days	Start	End	Year
6 days	January 4	January 9	1971
5 days	December 30	January 3	1912
5 days	January 22	January 26	1937
5 days	January 12	January 16	1963

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

# of days	Start	End	Year
4 days	January 5	January 8	1971
4 days	January 9	January 12	1964
3 days	January 6	January 8	1913
3 days	January 22	January 24	1937
3 days	January 4	January 6	1950
3 days	January 13	January 15	1963

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

# of days	Date	T of 1st day	T of 2nd day	T of 3rd day
3 days	January 6-8, 1913	17	16	19
2 days	January 7-8, 1971	19	20

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

# of days	Years		# of days	Years
39 days	1963-1964		21 days	1965-1966
30 days	1897-1898		18 days	1912-1913
29 days	1916-1917		16 days	1936-1937
24 days	1911-1912		16 days	1971-1972
24 days	1966-1967		14 days	1968-1969
21 days	1903-1904		12 days	1970-1971

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

# of days	Years		# of days	Years
15 days	1963-1964		8 days	1966-1967
10 days	1897-1898		7 days	1962-1963
9 days	1911-1912		6 days	1903-1904
9 days	1936-1937		6 days	1970-1971
8 days	1916-1917		5 days	1912-1913

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

# of days	Years		# of days	Years
5 days	1963-1964		3 days	1912-1913
4 days	1897-1898		3 days	1936-1937
4 days	1911-1912		3 days	1962-1963
4 days	1970-1971		2 days	1916-1917

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

# of days	Years		# of days	Years
3 days	1912-1913		1 day	1962-1963
2 days	1970-1971		1 day	1963-1964

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

# of days	Years		# of days	Years
0 days	1977-1978		0 days	1993-1994
0 days	1980-1981		0 days	1994-1995
0 days	1981-1982		1 day	1937-1938
0 days	1982-1983		1 day	1940-1941
0 days	1983-1984		1 day	1942-1943
0 days	1985-1986		1 day	1952-1953
0 days	1991-1992
0 days	1992-1993

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

# of days	Start	End	Year
14 days	August 18	August 31	1981
14 days	July 28	August 10	1995
11 days	July 18	July 28	1981
10 days	August 28	September 6	1983
10 days	July 5	July 14	1985
8 days	July 3	July 10	1981
8 days	July 31	August 7	1986
8 days	June 22	June 29	1988
8 days	June 24	July 1	1990
7 days	July 2	July 8	1973
7 days	July 28	August 3	1977
7 days	July 27	August 2	1980
7 days	August 24	August 30	1985
7 days	July 4	July 10	1988
7 days	July 14	July 20	1989
7 days	June 27	July 3	1994

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

# of days	Start	End	Year
40 days	July 7	August 15	1977
35 days	June 15	July 18	1988
34 days	July 30	September 1	1994
28 days	July 16	August 12	1980
27 days	July 28	August 23	1986
26 days	August 24	September 18	1983
25 days	July 20	August 13	1985
22 days	July 18	August 8	1983
21 days	July 31	August 20	1988
20 days	August 16	September 4	1981
19 days	July 23	August 10	1982
18 days	July 2	July19	1991
17 days	June 26	July 12	1984
17 days	July 29	August 14	1989

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

# of days	Year		# of days	Year
51 days	1981		26 days	1986
35 days	1983		23 days	1980
33 days	1977		23 days	1985
33 days	1989		19 days	1970
32 days	1994		18 days	1969
27 days	1982		17 days	1984
27 days	1991		17 days	1992
27 days	1995		15 days	1987

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

# of days	Year		# of days	Year
87 days	1981		60 days	1958
76 days	1977		60 days	1970
76 days	1985		59 days	1995
71 days	1983		57 days	1982
71 days	1989		57 days	1993
70 days	1994		54 days	1969
67 days	1986		54 days	1984
66 days	1991		52 days	1933
61 days	1992		49 days	1980

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

#of days	Date	Day 1	Day 2	Day 3	Day 4	Day 5	Day 6	Day7	Day 8
8 days	August 3-10 1995:	100	101	100	101	100	101	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 days	Year		# of days	Year
14 days	1995		5 days	1973
12 days	1989		5 days	1980
10 days	1990		5 days	1985
7 days	1985		5 days	1986
7 days	1994		4 days	1970
5 days	1969		4 days	1972

HIGHEST DAILY MEAN
1896-1995

Mean Temp	Date	Maximum Temp	Minimum Temp
107	June 26, 1990:	122	91
106	June 27, 1990:	118	93
104	June 25, 1990:	120	88

LOWEST DAILY MEAN
1896-1995

Temperature	Date	Maximum Temp	Minimum Temp
28	January 6 1913:	39	17
28	January 7 1913:	41	16
33	January 22 1937:	45	21
33	January 13 1963:	45	20
33	January 7 1971:	46	19

GREATEST DAILY TEMPERATURE RANGE
1896-1995

Temp Range	Date	Maximum Temp	Minimum Temp
48	June 13, 1917:	107	59
48	April 17, 1919:	96	48

LEAST DAILY TEMPERATURE RANGE
1896-1995

Temp Range	Date	Maximum Temp	Minimum Temp
3	December 10 1898:	36	33
3	November 26 1905:	60	57
3	October 24 1919:	62	59
3	February 3 1983:	52	49
3	November 25 1985:	61	58

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

	NORMAL	HIGHEST	YEAR	LOWEST	YEAR
	1961-1990	1899-1995		1899-1995
July	0	0	all	0	all
August	0	0	all	0	all
September	0	4	1965	0	most
October	17	88	1908	0	several
November	134	293	1922	36	1989
December	345	573	1911	122	1980
January	362	681	1937	110	1986
February	227	458	1939	27	1991
March	182	288	1952	6	1934
April	75	133	1965	0	several
May	8	55	1915	0	many
June	0	0	all	0	all
Season	1350	2062	1916-1917	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	HIGHEST	YEAR	LOWEST	YEAR
	1961-1990	1969-1995		1969-1995
January	8	10	1988	0	most
February	22	61	1991	0	several
March	95	210	1989	0	1973
April	222	459	1989	42	1975
May	436	688	1984	265	1971
June	696	873	1990	582	1969
July	884	1013	1989	833	1976
August	822	961	1981	763	1979
September	618	787	1983	525	1985
October	311	543	1988	151	1970
November	41	124	1988	4	1972
December	7	13	1980	0	most
Annual	4162	5245	1989	3651	1971

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	HIGHEST	YEAR	LOWEST	YEAR
	1961-1990	1951-1990		1951-1992
January	0	0	all	0	all
February	0	0	all	0	all
March	0	7	1986	0	most
April	9	84	1989	0	most
May	71	238	1984	3	1957
June	264	423	1990	41	1965
July	423	548	1989	222	1955
August	364	496	1981	183	1956
September	189	348	1983	65	1961 1964
October	24	150	1991	0	several
November	0	2	1988	0	most
December	0	0	all	0	all
Annual	1344	1934	1989	737	1964

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.