State Precipitation & Temperature Update for Arizona

Conditions through December 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 01/31/2008. The data are preliminary.


 

Precipitation Percentiles by Watershed (through December 2007)

 

Temperature Percentiles by Climate Division (through December 2007)


SHORT TERM CONDITIONS: 1-6 MONTHS

December was extremely wet everywhere in the state; between the 75th and 84th percentile in the southern watersheds; between the 89th and 95th percentile in the central watersheds; and between the 89th and 100th percentile in the northern watersheds. Most of the precipitation fell in a five day period from the 6th through the 11th, as part of a major winter storm that brought significant snowfall to the mountains. The series of cold fronts that passed through the state lowered temperatures dramatically from the previous month. November had been the 3rd warmest year since 1895, but December temperatures were near average along the lower Colorado River and well below average elsewhere, with Yavapai County at the 24th percentile. The three-month period of October through December had nearly average precipitation in the northern and southeastern watersheds, and well above average precipitation in the central and southwestern watersheds. The wet conditions are mostly a result of the very wet December across the state. The cold December, averaged with the very warm October and November, brought the three-month average temperatures down near the 80th percentile in most climate divisions. Even the hotter climate divisions of Gila, Maricopa and Pinal Counties fell below the 93rd percentile. The 6-month period precipitation was near average in the southeast, and well above average in all other watersheds. This period reflects both the wet monsoon and the wet early winter. The wet December brought the Virgin River watershed from the 3rd to the 17th percentile. The hot summer and fall have kept the six-month temperatures up above the 85th percentile everywhere in the state. The hottest conditions were still in the Maricopa-Pinal County climate division at the 96th percentile.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

100.00

CD1

45.13

Upper Colorado

89.19

CD2

36.28

Little Colorado

97.30

CD3

24.78

Verde

94.44

CD4

46.46

Bill Williams

89.19

CD5

44.25

Agua Fria

89.19

CD6

26.99

Lower Gila

89.19

CD7

30.97

Salt

91.89

 

Lower Colorado

83.78

 

Upper Gila

83.78

 

Santa Cruz

83.78

 

San Pedro

77.14

 

Willcox Playa

75.68

 

San Simon

83.78

 

White Water Draw

75.68

 

DECEMBER 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

50.00

CD1

82.30

Upper Colorado

40.54

CD2

80.53

Little Colorado

54.05

CD3

74.78

Verde

63.89

CD4

92.92

Bill Williams

54.05

CD5

79.20

Agua Fria

70.27

CD6

89.38

Lower Gila

75.68

CD7

81.42

Salt

70.27

 

Lower Colorado

70.27

 

Upper Gila

51.35

 

Santa Cruz

59.46

 

San Pedro

54.29

 

Willcox Playa

52.78

 

San Simon

72.97

 

White Water Draw

54.05

 

OCTOBER 2007 - DECEMBER 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

17.14

CD1

85.40

Upper Colorado

70.27

CD2

92.04

Little Colorado

75.68

CD3

92.04

Verde

77.78

CD4

93.81

Bill Williams

62.16

CD5

90.27

Agua Fria

59.46

CD6

96.46

Lower Gila

91.89

CD7

91.15

Salt

75.68

 

Lower Colorado

70.27

 

Upper Gila

56.76

 

Santa Cruz

54.05

 

San Pedro

48.57

 

Willcox Playa

50.00

 

San Simon

67.57

 

White Water Draw

52.78

 

JULY 2007 DECEMBER 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 is now about average for precipitation in most watersheds with the wet second half of the calendar year balancing out the dry first half of the calendar year. Notable exceptions are the very dry Virgin, Bill Williams and Agua Fria watersheds and the very wet lower Gila watershed. The past 12 months have continued to be very hot with temperatures above the 83rd percentile in all climate divisions.

 

The 24 month period is yet again the driest period, although now only 3 watersheds are below the 12th percentile, and five are near or above average for precipitation. The dry watersheds are toward the north half of the state, indicating that the 24-month deficit is due more to winter dryness than summer dryness. Temperatures are all above the 81st percentile with the southern 1/3 of the state above the 98th percentile.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

2.86

CD1

83.04

Upper Colorado

37.84

CD2

94.64

Little Colorado

48.65

CD3

91.96

Verde

43.24

CD4

91.96

Bill Williams

18.92

CD5

92.86

Agua Fria

24.32

CD6

96.43

Lower Gila

75.68

CD7

94.64

Salt

56.76

 

Lower Colorado

40.54

 

Upper Gila

56.76

 

Santa Cruz

35.14

 

San Pedro

40.54

 

Willcox Playa

54.05

 

San Simon

45.95

 

White Water Draw

59.46

 

JANUARY 2007 DECEMBER 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

11.76

CD1

81.98

Upper Colorado

27.78

CD2

93.69

Little Colorado

36.11

CD3

90.99

Verde

19.44

CD4

90.99

Bill Williams

8.33

CD5

92.79

Agua Fria

11.11

CD6

98.20

Lower Gila

44.44

CD7

99.10

Salt

27.78

 

Lower Colorado

22.22

 

Upper Gila

55.56

 

Santa Cruz

30.56

 

San Pedro

47.22

 

Willcox Playa

66.67

 

San Simon

16.67

 

White Water Draw

58.33

 

JANUARY 2006 DECEMBER 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 period has nine watersheds near normal for precipitation, and only three at or below the 20th percentile. The Santa Cruz and San Simon watersheds in southern Arizona have been extremely dry for the three year period, as has the Bill Williams in central Arizona. Again, temperatures over the three-year period are extremely high with only the northwest climate division below the 80th percentile, and the southern climate divisions above the 98th percentile.

 

The 48-month period again shows above average precipitation across the western part of the state, and near average precipitation in eastern and southern Arizona. The exceptions are the Santa Cruz and San Simon watersheds, both below the 15th percentile, and the San Pedro below the 30th percentile. There are still three climate divisions in the southern half of the state above the 96th percentile for temperature. Only the northwest climate division, most of Mohave County, is below the 78th percentile.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

51.52

CD1

79.09

Upper Colorado

45.71

CD2

92.73

Little Colorado

45.71

CD3

91.82

Verde

37.14

CD4

94.55

Bill Williams

17.14

CD5

89.09

Agua Fria

31.43

CD6

98.18

Lower Gila

54.29

CD7

100.00

Salt

45.71

 

Lower Colorado

48.57

 

Upper Gila

51.43

 

Santa Cruz

20.00

 

San Pedro

34.29

 

Willcox Playa

48.57

 

San Simon

17.14

 

White Water Draw

57.14

 

JANUARY 2005 DECEMBER 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

64.52

CD1

77.06

Upper Colorado

67.65

CD2

90.83

Little Colorado

35.29

CD3

91.74

Verde

55.88

CD4

96.33

Bill Williams

41.18

CD5

88.07

Agua Fria

41.18

CD6

97.25

Lower Gila

61.76

CD7

99.08

Salt

50.00

 

Lower Colorado

67.65

 

Upper Gila

44.12

 

Santa Cruz

8.82

 

San Pedro

29.41

 

Willcox Playa

52.94

 

San Simon

14.71

 

White Water Draw

55.88

 

JANUARY 2004 DECEMBER 2007 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

January 2008 Arizona Drought Update based on precipitation data through December 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

December was extremely wet everywhere in the state; between the 75th and 84th percentile in the southern watersheds; between the 89th and 95th percentile in the central watersheds; and between the 89th and 100th percentile in the northern watersheds. Most of the precipitation fell in a five day period from the 6th through the 11th, as part of a major winter storm that brought significant snowfall to the mountains. The series of cold fronts that passed through the state lowered temperatures dramatically from the previous month. November had been the 3rd warmest year since 1895, but December temperatures were near average along the lower Colorado River and well below average elsewhere, with Yavapai County at the 24th percentile.

 

The 3-month period of October through December had nearly average precipitation in the northern and southeastern watersheds, and well above average precipitation in the central and southwestern watersheds. The wet conditions are mostly a result of the very wet December across the state. The cold December, averaged with the very warm October and November, brought the three-month average temperatures down near the 80th percentile in most climate divisions. Even the hotter climate divisions of Gila, Maricopa and Pinal Counties fell below the 93rd percentile.

 

The 6-month period precipitation was near average in the southeast, and well above average in all other watersheds. This period reflects both the wet monsoon and the wet early winter. The wet December brought the Virgin River watershed from the 3rd to the 17th percentile. The hot summer and fall have kept the six-month temperatures up above the 85th percentile everywhere in the state. The hottest conditions were still in the Maricopa-Pinal County climate division at the 96th percentile.

 

The 12-month period is now about average for precipitation in most watersheds with the wet second half of the calendar year balancing out the dry first half of the calendar year. Notable exceptions are the very dry Virgin, Bill Williams and Agua Fria watersheds and the very wet lower Gila watershed. The past 12 months have continued to be very hot with temperatures above the 83rd percentile in all climate divisions.

 

The 24 month period is yet again the driest period, although now only 3 watersheds are below the 12th percentile, and five are near or above average for precipitation. The dry watersheds are toward the north half of the state, indicating that the 24-month deficit is due more to winter dryness than summer dryness. Temperatures are all above the 81st percentile with the southern 1/3 of the state above the 98th percentile.

 

The 36-month period has nine watersheds near normal for precipitation, and only three at or below the 20th percentile. The Santa Cruz and San Simon watersheds in southern Arizona have been extremely dry for the three year period, as has the Bill Williams in central Arizona. Again, temperatures over the three-year period are extremely high with only the northwest climate division below the 80th percentile, and the southern climate divisions above the 98th percentile.

 

The 48-month period again shows above average precipitation across the western part of the state, and near average precipitation in eastern and southern Arizona. The exceptions are the Santa Cruz and San Simon watersheds, both below the 15th percentile, and the San Pedro below the 30th percentile. There are still three climate divisions in the southern half of the state above the 96th percentile for temperature. Only the northwest climate division, most of Mohave County, is below the 78th percentile.