State Precipitation & Temperature Update for Arizona

Conditions through October 2007

Precipitation is monitored for the state of Arizona across the 15 major watersheds (see map left). From the stations within each watershed, mean values of precipitation for the watershed as a whole are computed. These mean values are ranked against the monthly mean values for the period of 1971-present. The rankings are then divided by the number of years of data and multiplied by 100% to create percentiles.

 

Here, precipitation percentile values for the most recent month, along with previous 3-, 6-, 12-, 24-, 36-, and 48-month total are shown for each watershed. Low percentile values (brown shading) indicate dry conditions while high values (green shading) indicate wet conditions. For example, a precipitation total that falls at the 100th percentile means that it is the highest precipitation total for the 1971-present period.

 

Temperature is monitored for the state of Arizona across seven climate divisions (see map left). From the stations within each climate division, mean values of temperature for the climate division as a whole are computed. These mean values are ranked against the monthly mean values for the period of 1895-present. The rankings are then divided by the number of years of data and multiplied by 100% to create percentiles.

 

Here, temperature percentile values for the most recent month, along with previous 3-, 6-, 12-, 24-, 36-, and 48-month averages are shown for each climate division. Low percentile values (blue shading) indicate cool conditions while high values (orange/red shading) indicate hot conditions. For example, a temperature that falls at the 100th percentile means that it is the highest average temperature for the 1895-present period.

 

The maps of the seven periods for precipitation and temperature are shown below, with tables of the percentile values and descriptive text following the maps. Current update is 12/02/2007. The data are preliminary.


 

Precipitation Percentiles by Watershed (through October 2007)

 

Temperature Percentiles by Climate Division (through October 2007)


SHORT TERM CONDITIONS: 1-6 MONTHS

October was extremely dry, with all watersheds, except the lower Colorado, below the 22nd percentile. The lower Colorado typically receives almost no rainfall in October, so their percentile was almost average. For the second month in a row, temperatures were somewhat cooler than previous months. The northern counties were below the 70th percentile and the warmest, in the southeast, were between the 76th and 85th percentile. The lack of fall rainfall will impact the spring run-off, as dry soil tends to absorb the snowmelt, reducing the flow into the reservoirs. The 3-month period of August through October, was near average on the upper Colorado, but below average everywhere else, because the tail end of the monsoon was fairly dry, and the fall has been dry as well. The clear skies and dry weather have pushed the temperatures above the 81st percentile everywhere in the state. Maricopa and Pinal counties were the warmest and Yavapai County was the coolest. The 6-month period rainfall was near average for much of the state, and below average in the south central watersheds. The lower Gila had slightly above average rainfall in the past 6 months, due to heavy July precipitation in Gila Bend, Laveen, and Wickenburg. Temperatures in the northern and western part of the state were around the 93rd percentile, and in the southeastern part of the state the temperatures were between the 95th and 98th percentile. Some early frontal systems brought cooler weather to the higher elevations, and the first freezing temperature was reported in September, and nighttime temperatures have dropped below freezing regularly at the higher elevations.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

5.41

CD1

65.93

Upper Colorado

10.81

CD2

69.47

Little Colorado

16.22

CD3

56.64

Verde

10.81

CD4

84.51

Bill Williams

21.62

CD5

61.95

Agua Fria

10.81

CD6

82.30

Lower Gila

13.51

CD7

76.99

Salt

13.51

 

Lower Colorado

45.95

 

Upper Gila

10.81

 

Santa Cruz

16.22

 

San Pedro

13.51

 

Willcox Playa

18.92

 

San Simon

13.51

 

White Water Draw

16.22

 

OCTOBER 2007: percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

2.86

CD1

87.17

Upper Colorado

48.65

CD2

85.84

Little Colorado

32.43

CD3

81.86

Verde

32.43

CD4

93.81

Bill Williams

21.62

CD5

85.40

Agua Fria

8.11

CD6

95.58

Lower Gila

35.14

CD7

87.61

Salt

18.92

 

Lower Colorado

18.92

 

Upper Gila

32.43

 

Santa Cruz

16.22

 

San Pedro

21.62

 

Willcox Playa

43.24

 

San Simon

8.11

 

White Water Draw

43.24

 

AUGUST 2006 - OCTOBER 2007 (3-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

2.86

CD1

92.04

Upper Colorado

59.46

CD2

92.92

Little Colorado

51.35

CD3

95.58

Verde

56.76

CD4

97.35

Bill Williams

56.76

CD5

93.81

Agua Fria

32.43

CD6

97.35

Lower Gila

78.38

CD7

95.58

Salt

51.35

 

Lower Colorado

59.46

 

Upper Gila

43.24

 

Santa Cruz

37.84

 

San Pedro

37.84

 

Willcox Playa

48.65

 

San Simon

32.43

 

White Water Draw

47.22

 

MAY 2006 OCTOBER 2007 (6-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

 

INTERMEDIATE TERM CONDITIONS: 12-24 MONTHS

The 12-month period has been extremely dry in most of the state. Three watersheds in the southern part of the state were between the 8th and 14th percentile, and the other 12 watersheds were all below the 23rd percentile, putting this year on the dry side of the drought tally. The entire state continued to have temperatures above the 85th percentile during the previous 12 months. Many locations had daily records tied or broken for both maximum and minimum temperatures.

 

The two year period continues to show the driest conditions of all periods. The last wet year was 2005, with high precipitation totals for both winter and summer in most places. Since then, we have had two very dry years, punctuated with an occasional wet month, usually in summer. The Virgin, Bill Williams, Agua Fria, Salt, Santa Cruz, and San Simon watersheds are all below the 9th percentile for the 24-month period. Exceptions are WIllcox Playa and White Water Draw in the southeast, which have benefited from two moderately wet monsoons, bringing them above the 42nd percentile. Temperatures continue to be above the 81st percentile, with the southern and southeastern counties have the hottest conditions.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

2.94

CD1

87.50

Upper Colorado

22.22

CD2

91.07

Little Colorado

16.67

CD3

93.75

Verde

11.11

CD4

94.64

Bill Williams

11.11

CD5

88.39

Agua Fria

5.56

CD6

94.64

Lower Gila

33.33

CD7

95.54

Salt

5.56

 

Lower Colorado

19.44

 

Upper Gila

13.89

 

Santa Cruz

8.33

 

San Pedro

11.11

 

Willcox Playa

28.57

 

San Simon

8.33

 

White Water Draw

38.89

 

NOVEMBER 2006 OCTOBER 2007 (12-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

3.12

CD1

81.08

Upper Colorado

11.43

CD2

92.79

Little Colorado

17.14

CD3

91.89

Verde

11.43

CD4

93.69

Bill Williams

2.86

CD5

91.89

Agua Fria

5.71

CD6

96.40

Lower Gila

11.43

CD7

100.00

Salt

8.57

 

Lower Colorado

17.14

 

Upper Gila

17.14

 

Santa Cruz

5.71

 

San Pedro

22.86

 

Willcox Playa

45.71

 

San Simon

5.71

 

White Water Draw

42.86

 

NOVEMBER 2005 OCTOBER 2007 (24-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

LONG TERM CONDITIONS: 36-48 MONTHS

The 36-month precipitation period continues to show the results of the wet winter of 2004-05 in northern and western Arizona. The central and eastern watersheds are near average, and the southern watersheds are well below-average, now below the 9th percentile. The two more recent dry years are gradually bringing the 36-month percentiles down. Temperatures over the 3-year period range from the 77th percentile to the 100th percentile in the southeast. This pattern has not changed in nearly a year, showing that even the monsoon, which generally lowers temperatures for two months due to cloudiness and cooling, does not have much impact on a 36 month record.

 

The 48-month period precipitation is also above average across the northern part of the state, and well below average in south central Arizona. Three watersheds are above the 66th percentile, mostly in the north; three more are near normal, averaging at the 48th percentile; five are below the 25th percentile; and 2 are below the 13th percentile. The warm conditions continue with two of the southern climate divisions above the 96th percentile for temperature, and the southeast climate division at the 100th percentile again.

 


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

62.50

CD1

77.27

Upper Colorado

58.82

CD2

91.82

Little Colorado

35.29

CD3

90.00

Verde

44.12

CD4

94.55

Bill Williams

32.35

CD5

88.18

Agua Fria

38.24

CD6

98.18

Lower Gila

52.94

CD7

100.00

Salt

35.29

 

Lower Colorado

64.71

 

Upper Gila

29.41

 

Santa Cruz

8.82

 

San Pedro

29.41

 

Willcox Playa

38.24

 

San Simon

8.82

 

White Water Draw

47.06

 

NOVEMBER 2004 OCTOBER 2007 (36-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

70.00

CD1

77.06

Upper Colorado

66.67

CD2

90.83

Little Colorado

27.27

CD3

90.83

Verde

48.48

CD4

95.41

Bill Williams

33.33

CD5

88.07

Agua Fria

21.21

CD6

94.50

Lower Gila

45.45

CD7

100.00

Salt

24.24

 

Lower Colorado

69.70

 

Upper Gila

33.33

 

Santa Cruz

6.06

 

San Pedro

21.21

 

Willcox Playa

39.39

 

San Simon

12.12

 

White Water Draw

51.52

 

NOVEMBER 2003 OCTOBER 2007 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

November 2007 Arizona Drought Update based on Precipitation (data through October 2007)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods.

 

SUMMARY

October was extremely dry, with all watersheds, except the lower Colorado, below the 22nd percentile. The lower Colorado typically receives almost no rainfall in October, so their percentile was almost average. For the second month in a row, temperatures were somewhat cooler than previous months. The northern counties were below the 70th percentile and the warmest, in the southeast, were between the 76th and 85th percentile. The lack of fall rainfall will impact the spring run-off, as dry soil tends to absorb the snowmelt, reducing the flow into the reservoirs.

 

The 3-month period of August through October, was near average on the upper Colorado, but below average everywhere else, because the tail end of the monsoon was fairly dry, and the fall has been dry as well. The clear skies and dry weather have pushed the temperatures above the 81st percentile everywhere in the state. Maricopa and Pinal counties were the warmest and Yavapai County was the coolest.

 

The 6-month period rainfall was near average for much of the state, and below average in the south central watersheds. The lower Gila had slightly above average rainfall in the past 6 months, due to heavy July precipitation in Gila Bend, Laveen, and Wickenburg. Temperatures in the northern and western part of the state were around the 93rd percentile, and in the southeastern part of the state the temperatures were between the 95th and 98th percentile. Some early frontal systems brought cooler weather to the higher elevations, and the first freezing temperature was reported in September, and nighttime temperatures have dropped below freezing regularly at the higher elevations.

 

The 12-month period has been extremely dry in most of the state. Three watersheds in the southern part of the state were between the 8th and 14th percentile, and the other 12 watersheds were all below the 23rd percentile, putting this year on the dry side of the drought tally. The entire state continued to have temperatures above the 85th percentile during the previous 12 months. Many locations had daily records tied or broken for both maximum and minimum temperatures.

 

The two year period continues to show the driest conditions of all periods. The last wet year was 2005, with high precipitation totals for both winter and summer in most places. Since then, we have had two very dry years, punctuated with an occasional wet month, usually in summer. The Virgin, Bill Williams, Agua Fria, Salt, Santa Cruz, and San Simon watersheds are all below the 9th percentile for the 24-month period. Exceptions are WIllcox Playa and White Water Draw in the southeast, which have benefited from two moderately wet monsoons, bringing them above the 42nd percentile. Temperatures continue to be above the 81st percentile, with the southern and southeastern counties have the hottest conditions.

 

The 36-month precipitation period continues to show the results of the wet winter of 2004-05 in northern and western Arizona. The central and eastern watersheds are near average, and the southern watersheds are well below-average, now below the 9th percentile. The two more recent dry years are gradually bringing the 36-month percentiles down. Temperatures over the 3-year period range from the 77th percentile to the 100th percentile in the southeast. This pattern has not changed in nearly a year, showing that even the monsoon, which generally lowers temperatures for two months due to cloudiness and cooling, does not have much impact on a 36 month record.

 

The 48-month period precipitation is also above average across the northern part of the state, and well below average in south central Arizona. Three watersheds are above the 66th percentile, mostly in the north; three more are near normal, averaging at the 48th percentile; five are below the 25th percentile; and 2 are below the 13th percentile. The warm conditions continue with two of the southern climate divisions above the 96th percentile for temperature, and the southeast climate division at the 100th percentile again.