State Precipitation & Temperature Update for Arizona

Conditions through November 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 12/26/2007. The data are preliminary.


 

Precipitation Percentiles by Watershed (through November 2007)

 

Temperature Percentiles by Climate Division (through November 2007)


SHORT TERM CONDITIONS: 1-6 MONTHS

November was dry in the northern half of the state and near or slightly above average for the southern half of the state. After 28 days of dry conditions, most of the state received two days of moderate, steady rainfall at the end of the month that prevented November from being one of the driest on record. The big winners were the lower Gila and San Pedro watersheds in the south, as the warm storm system moved northward through Arizona from the Gulf of California. Due to the consistent high pressure position over the western US, November was in the top 3% warmest since 1895, everywhere in the state. The three-month period of September through November was unusually dry everywhere in the state, but especially so across the northern half of the state, on the Colorado Plateau. The southern half of the state benefited from the end of the monsoon in September, which brought a few storms to the southern watersheds. The clear skies and dry weather during the fall have pushed the temperatures above the 91st percentile everywhere in the state. The southern half of the state was above the 97th percentile. The 6-month period rainfall was near average for most of the state. The lower Gila had above-average rainfall, while the Salt and Agua Fria watersheds in central Arizona, and the Santa Cruz and San Simon watersheds in southern Arizona, had slightly below-average rainfall. The Virgin River in northwest Arizona was very dry, below the 3rd percentile. Temperatures everywhere except the lower Colorado River were above the 95th percentile for the six month period. The lower Colorado River was still warm, with temperatures between the 86th and 94th percentiles.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

4.17

CD1

98.23

Upper Colorado

10.81

CD2

100.00

Little Colorado

18.92

CD3

97.35

Verde

35.14

CD4

98.23

Bill Williams

16.22

CD5

98.23

Agua Fria

56.76

CD6

100.00

Lower Gila

78.38

CD7

97.35

Salt

45.95

 

Lower Colorado

45.95

 

Upper Gila

40.54

 

Santa Cruz

56.76

 

San Pedro

70.27

 

Willcox Playa

51.39

 

San Simon

48.65

 

White Water Draw

56.76

 

NOVEMBER 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

5.71

CD1

91.15

Upper Colorado

10.81

CD2

94.69

Little Colorado

8.11

CD3

92.92

Verde

24.32

CD4

94.69

Bill Williams

16.22

CD5

91.15

Agua Fria

24.32

CD6

97.35

Lower Gila

40.54

CD7

97.35

Salt

21.62

 

Lower Colorado

32.43

 

Upper Gila

16.22

 

Santa Cruz

24.32

 

San Pedro

27.03

 

Willcox Playa

22.22

 

San Simon

24.32

 

White Water Draw

21.62

 

SEPTEMBER 2006 - NOVEMBER 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

86.73

Upper Colorado

43.24

CD2

98.23

Little Colorado

40.54

CD3

95.58

Verde

51.35

CD4

96.46

Bill Williams

43.24

CD5

93.81

Agua Fria

29.73

CD6

99.12

Lower Gila

86.49

CD7

99.12

Salt

35.14

 

Lower Colorado

56.76

 

Upper Gila

40.54

 

Santa Cruz

37.84

 

San Pedro

45.95

 

Willcox Playa

44.44

 

San Simon

32.43

 

White Water Draw

50.00

 

JUNE 2006 NOVEMBER 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 continues to be extremely dry across the entire state. Four watersheds in the central part of the state, and one on the southern border, were below the 11th percentile. All but one of the other 10 watersheds were below the 39th percentile. Statewide temperatures were above the 85th percentile during the previous 12 months, while the Colorado Plateau and southern Arizona were above the 96th percentile.

 

The driest interval remains the 24 month period, with 12 of 15 watersheds below the 20th percentile. Eight watersheds in northwest, central, and south central Arizona are below the 15th percentile. Only the San Pedro, Willcox, and White Water Draw watersheds have had near normal precipitation in the past two years. In the long term, only Northwestern Arizona has remained below the 81st percentile for temperature. The rest of the state has been above the 91st percentile, and the two southern climate divisions were above the 98th percentile for temperature.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

2.94

CD1

85.71

Upper Colorado

25.00

CD2

96.43

Little Colorado

13.89

CD3

94.64

Verde

11.11

CD4

91.07

Bill Williams

11.11

CD5

90.18

Agua Fria

11.11

CD6

96.43

Lower Gila

55.56

CD7

96.43

Salt

16.67

 

Lower Colorado

16.67

 

Upper Gila

30.56

 

Santa Cruz

16.67

 

San Pedro

19.44

 

Willcox Playa

30.56

 

San Simon

11.11

 

White Water Draw

38.89

 

DECEMBER 2006 NOVEMBER 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

3.03

CD1

80.18

Upper Colorado

14.29

CD2

93.69

Little Colorado

17.14

CD3

91.89

Verde

11.43

CD4

93.69

Bill Williams

2.86

CD5

93.69

Agua Fria

5.71

CD6

98.20

Lower Gila

17.14

CD7

100.00

Salt

11.43

 

Lower Colorado

20.00

 

Upper Gila

20.00

 

Santa Cruz

8.57

 

San Pedro

34.29

 

Willcox Playa

48.57

 

San Simon

8.57

 

White Water Draw

42.86

 

DECEMBER 2005 NOVEMBER 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 is the closest to normal of all time periods. It combines two dry years (2004 and 2006) with one very wet year (2005) Most of western Arizona is near average, while eastern Arizona is below average at the 26th to 39th percentile, and southern Arizona is much below average at the 8th to 12th percentile. This shows that although a good wet year is helpful, it cannot erase the deficit. Temperatures over the three-year period are similar to the two-year period, with the northwest below the 79th percentile, and the others all above the 88th percentile. Southern Arizona has been extremely warm the past three years, above the 98th percentile.

 

The 48-month period precipitation is also near average across the western part of the state, and well below-average in eastern and southern Arizona. The Virgin watershed in the northwest and the lower Colorado watershed in the southwest had above-average precipitation for the four-year period. Ten of the fifteen watersheds were well below the 50th percentile. Three climate divisions, all in the southern half of the state, were above the 96th percentile for temperature, and two were above the 99th percentile for the four-year period. The warm temperatures have added to the evaporative demand, enhancing the dry conditions.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

46.88

CD1

78.18

Upper Colorado

47.06

CD2

93.64

Little Colorado

29.41

CD3

92.73

Verde

41.18

CD4

93.64

Bill Williams

17.65

CD5

88.18

Agua Fria

29.41

CD6

98.18

Lower Gila

50.00

CD7

100.00

Salt

38.24

 

Lower Colorado

55.88

 

Upper Gila

35.29

 

Santa Cruz

11.76

 

San Pedro

26.47

 

Willcox Playa

41.18

 

San Simon

8.82

 

White Water Draw

44.12

 

DECEMBER 2004 NOVEMBER 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

63.33

CD1

77.06

Upper Colorado

57.58

CD2

89.91

Little Colorado

21.21

CD3

92.66

Verde

42.42

CD4

96.33

Bill Williams

30.30

CD5

88.99

Agua Fria

21.21

CD6

99.08

Lower Gila

48.48

CD7

100.00

Salt

24.24

 

Lower Colorado

63.64

 

Upper Gila

33.33

 

Santa Cruz

6.06

 

San Pedro

24.24

 

Willcox Playa

36.36

 

San Simon

9.09

 

White Water Draw

45.45

 

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

 

December 2007 Arizona Drought Update based on precipitation data through November 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

November was dry in the northern half of the state and near or slightly above average for the southern half of the state. After 28 days of dry conditions, most of the state received two days of moderate, steady rainfall at the end of the month that prevented November from being one of the driest on record. The big winners were the lower Gila and San Pedro watersheds in the south, as the warm storm system moved northward through Arizona from the Gulf of California. Due to the consistent high pressure position over the western US, November was in the top 3% warmest since 1895, everywhere in the state.

 

The 3-month period of September through November was unusually dry everywhere in the state, but especially so across the northern half of the state, on the Colorado Plateau. The southern half of the state benefited from the end of the monsoon in September, which brought a few storms to the southern watersheds. The clear skies and dry weather during the fall have pushed the temperatures above the 91st percentile everywhere in the state. The southern half of the state was above the 97th percentile.

 

The 6-month period rainfall was near average for most of the state. The lower Gila had above-average rainfall, while the Salt and Agua Fria watersheds in central Arizona, and the Santa Cruz and San Simon watersheds in southern Arizona, had slightly below-average rainfall. The Virgin River in northwest Arizona was very dry, below the 3rd percentile. Temperatures everywhere except the lower Colorado River were above the 95th percentile for the six month period. The lower Colorado River was still warm, with temperatures between the 86th and 94th percentiles.

 

The 12-month period continues to be extremely dry across the entire state. Four watersheds in the central part of the state, and one on the southern border, were below the 11th percentile. All but one of the other 10 watersheds were below the 39th percentile. Statewide temperatures were above the 85th percentile during the previous 12 months, while the Colorado Plateau and southern Arizona were above the 96th percentile.

 

The driest interval remains the 24 month period, with 12 of 15 watersheds below the 20th percentile. Eight watersheds in northwest, central, and south central Arizona are below the 15th percentile. Only the San Pedro, Willcox, and White Water Draw watersheds have had near normal precipitation in the past two years. In the long term, only Northwestern Arizona has remained below the 81st percentile for temperature. The rest of the state has been above the 91st percentile, and the two southern climate divisions were above the 98th percentile for temperature.

 

The 36-month precipitation period is the closest to normal of all time periods. It combines two dry years (2004 and 2006) with one very wet year (2005) Most of western Arizona is near average, while eastern Arizona is below average at the 26th to 39th percentile, and southern Arizona is much below average at the 8th to 12th percentile. This shows that although a good wet year is helpful, it cannot erase the deficit. Temperatures over the three-year period are similar to the two-year period, with the northwest below the 79th percentile, and the others all above the 88th percentile. Southern Arizona has been extremely warm the past three years, above the 98th percentile.

 

The 48-month period precipitation is also near average across the western part of the state, and well below-average in eastern and southern Arizona. The Virgin watershed in the northwest and the lower Colorado watershed in the southwest had above-average precipitation for the four-year period. Ten of the fifteen watersheds were well below the 50th percentile. Three climate divisions, all in the southern half of the state, were above the 96th percentile for temperature, and two were above the 99th percentile for the four-year period. The warm temperatures have added to the evaporative demand, enhancing the dry conditions.