State Precipitation & Temperature Update for Arizona

Conditions through March 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 4/25/2007. The data are preliminary, and some data are missing from the Upper Colorado and Santa Cruz watersheds.


 

Precipitation Percentiles by Watershed (through March 2007)

 

Temperature Percentiles by Climate Division (through March 2007)


SHORT TERM CONDITIONS: 1-6 MONTHS

March precipitation was below average across the northern half of the state, near normal in the southwest and above average in the southeast watersheds. The near average precipitation in the Bill Williams and Lower Colorado watersheds will help offset extremely dry conditions the previous two months. The high temperatures of March (all watersheds were above the 89th percentile) melted virtually all of the snowpack around the state, and caused much of the precipitation to fall as rain rather than snow. The 3-month period of January through March was below the 25th percentile for the upper, lower and Little Colorado watersheds, as well as the Bill Williams in west central Arizona. The central and southern watersheds were also dry, with only White Water Draw above the 56th percentile. The typical winter storm track is across the northern half to two-thirds of the state, while an El Nio winter generally brings moisture to the central and southern watersheds. This year we saw neither the usual winter pattern nor the typical El Nio pattern. Although January was much colder than normal, both February and March were warmer than average, pushing the 3-month temperatures above the 50th percentile in all climate divisions. Fall and winter precipitation, represented by the 6-month period of October through March, was extremely dry, below the 44th percentile in all watersheds, with the upper Colorado being the wettest. The Santa Cruz and San Simon watersheds were the driest at the 14th percentile. In the six-month period, temperatures across the state were well above average, with the cooler areas in the Northeast plateau and the southwest.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

32.43

CD1

94.69

Upper Colorado

37.84

CD2

93.81

Little Colorado

21.62

CD3

92.04

Verde

29.73

CD4

97.35

Bill Williams

43.24

CD5

92.04

Agua Fria

43.24

CD6

92.04

Lower Gila

54.05

CD7

89.38

Salt

32.43

 

Lower Colorado

54.05

 

Upper Gila

62.16

 

Santa Cruz

51.35

 

San Pedro

64.86

 

Willcox Playa

78.38

 

San Simon

48.65

 

White Water Draw

83.78

 

MARCH 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

19.44

CD1

85.84

Upper Colorado

21.62

CD2

69.47

Little Colorado

25.00

CD3

66.37

Verde

27.03

CD4

84.96

Bill Williams

18.92

CD5

65.93

Agua Fria

35.14

CD6

84.96

Lower Gila

35.14

CD7

50.44

Salt

27.03

 

Lower Colorado

21.62

 

Upper Gila

48.65

 

Santa Cruz

29.73

 

San Pedro

51.35

 

Willcox Playa

55.56

 

San Simon

27.03

 

White Water Draw

63.89

 

JANUARY 2006 - MARCH 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

23.53

CD1

81.42

Upper Colorado

44.44

CD2

65.49

Little Colorado

25.71

CD3

70.35

Verde

28.57

CD4

76.11

Bill Williams

22.22

CD5

71.24

Agua Fria

22.22

CD6

80.53

Lower Gila

22.22

CD7

82.30

Salt

22.22

 

Lower Colorado

22.22

 

Upper Gila

36.11

 

Santa Cruz

13.89

 

San Pedro

32.35

 

Willcox Playa

31.43

 

San Simon

13.89

 

White Water Draw

40.00

 

OCTOBER 2006 MARCH 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 western half of the state continues to be very dry for the 12 month period that began in April of 2006, with only the highest elevation watersheds of the Salt, upper Gila, Little Colorado and southeastern Arizona experiencing near to above average precipitation. Much of that 12-month precipitation was the result of a wet monsoon in those areas. The wettest watersheds were the San Pedro and Willcox, just above the 62nd percentile. Temperatures for the previous 12 months continue to be well above average, with all climate division above the 80th percentile.

The two-year period map again shows the longer term drought condition. It seems that an occasional wet season, such as the winter of 2005 is completely offset by an exceptionally dry season, such as the winter of 2006, within the two year window. This alternating of wet and dry years prevents the wet years from being effective in alleviating the drought. The wettest watersheds are at the 40th percentile, and the driest are below the 3rd percentile. For temperature, all divisions except the northwest are above the 85th percentile, exacerbating the dry conditions. Again, the southeast climate division is the hot spot at the 100th percentile.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

17.65

CD1

83.04

Upper Colorado

30.56

CD2

82.14

Little Colorado

41.67

CD3

90.18

Verde

27.78

CD4

80.36

Bill Williams

8.33

CD5

91.96

Agua Fria

27.78

CD6

92.86

Lower Gila

27.78

CD7

96.43

Salt

30.56

 

Lower Colorado

33.33

 

Upper Gila

55.56

 

Santa Cruz

36.11

 

San Pedro

66.67

 

Willcox Playa

62.86

 

San Simon

22.22

 

White Water Draw

60.00

 

APRIL 2006 MARCH 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

36.36

CD1

73.87

Upper Colorado

11.43

CD2

88.29

Little Colorado

5.71

CD3

85.59

Verde

8.57

CD4

92.79

Bill Williams

2.86

CD5

86.49

Agua Fria

2.86

CD6

93.69

Lower Gila

8.57

CD7

100.00

Salt

2.86

 

Lower Colorado

37.14

 

Upper Gila

17.14

 

Santa Cruz

14.29

 

San Pedro

34.29

 

Willcox Playa

40.00

 

San Simon

5.71

 

White Water Draw

40.00

 

APRIL 2005 MARCH 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 has now fallen below the 21st percentile for three watersheds in the south central desert, and the Little Colorado watersheds is below the 40th percentile. Only the Virgin, upper, and lower Colorado are above the 60th percentile. The 36-month-temperature pattern remains unchanged for the past 3 months, with Gila County and the southeast climate division above the 95th percentile for temperature, and only the northwest below the 74th percentile.

 

The 48-month precipitation pattern shows the eastern parts of the state below the 25th percentile, and the western desert only slightly better off just below the 40th percentile. The upper and lower Colorado River basins are near to slightly above average. Unfortunately, the long-term temperature pattern remains unchanged, with all areas of the state above the 77th percentile, with the hottest temperatures in Gila County and the southeast climate division, both still above the 96th percentile.

 

 


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

84.38

CD1

73.18

Upper Colorado

67.65

CD2

88.18

Little Colorado

38.24

CD3

86.82

Verde

55.88

CD4

95.45

Bill Williams

52.94

CD5

86.36

Agua Fria

44.12

CD6

90.91

Lower Gila

52.94

CD7

98.18

Salt

41.18

 

Lower Colorado

79.41

 

Upper Gila

47.06

 

Santa Cruz

5.88

 

San Pedro

20.59

 

Willcox Playa

41.18

 

San Simon

11.76

 

White Water Draw

50.00

 

APRIL 2004 MARCH 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

-99.99

CD1

77.06

Upper Colorado

48.48

CD2

89.91

Little Colorado

21.21

CD3

91.74

Verde

30.30

CD4

96.33

Bill Williams

33.33

CD5

89.45

Agua Fria

21.21

CD6

93.58

Lower Gila

39.39

CD7

100.00

Salt

24.24

 

Lower Colorado

66.67

 

Upper Gila

21.21

 

Santa Cruz

12.12

 

San Pedro

18.18

 

Willcox Playa

18.18

 

San Simon

21.21

 

White Water Draw

36.36

 

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

 


April 2007 Arizona Drought Update based on Precipitation (data through March 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

March - precipitation was below average across the northern half of the state, near normal in the southwest and above average in the southeast watersheds. The near average precipitation in the Bill Williams and Lower Colorado watersheds will help offset extremely dry conditions the previous two months. The high temperatures of March (all watersheds were above the 89th percentile) melted virtually all of the snowpack around the state, and caused much of the precipitation to fall as rain rather than snow.

 

Three-month period The 3-month period of January through March was below the 25th percentile for the upper, lower and Little Colorado watersheds, as well as the Bill Williams in west central Arizona. The central and southern watersheds were also dry, with only White Water Draw above the 56th percentile. The typical winter storm track is across the northern half to two-thirds of the state, while an El Nio winter generally brings moisture to the central and southern watersheds. This year we saw neither the usual winter pattern nor the typical El Nio pattern. Although January was much colder than normal, both February and March were warmer than average, pushing the 3-month temperatures above the 50th percentile in all climate divisions.

 

Six-month period Fall and winter precipitation, represented by the 6-month period of October through March, was extremely dry, below the 44th percentile in all watersheds, with the upper Colorado being the wettest. The Santa Cruz and San Simon watersheds were the driest at the 14th percentile. In the six-month period, temperatures across the state were well above average, with the cooler areas in the Northeast plateau and the southwest.

 

Twelve-month period The western half of the state continues to be very dry for the 12 month period that began in April of 2006, with only the highest elevation watersheds of the Salt, upper Gila, Little Colorado and southeastern Arizona experiencing near to above average precipitation. Much of that 12-month precipitation was the result of a wet monsoon in those areas. The wettest watersheds were the San Pedro and Willcox, just above the 62nd percentile. Temperatures for the previous 12 months continue to be well above average, with all climate division above the 80th percentile.

 

Two-year period - The two-year period map again shows the longer term drought condition. It seems that an occasional wet season, such as the winter of 2005 is completely offset by an exceptionally dry season, such as the winter of 2006, within the two year window. This alternating of wet and dry years prevents the wet years from being effective in alleviating the drought. The wettest watersheds are at the 40th percentile, and the driest are below the 3rd percentile. For temperature, all divisions except the northwest are above the 85th percentile, exacerbating the dry conditions. Again, the southeast climate division is the hot spot at the 100th percentile.

 

Three-year period - The 36-month precipitation has now fallen below the 21st percentile for three watersheds in the south central desert, and the Little Colorado watersheds is below the 40th percentile. Only the Virgin, upper, and lower Colorado are above the 60th percentile. The 36-month-temperature pattern remains unchanged for the past 3 months, with Gila County and the southeast climate division above the 95th percentile for temperature, and only the northwest below the 74th percentile.

 

Four-year period - The 48-month precipitation pattern shows the eastern parts of the state below the 25th percentile, and the western desert only slightly better off just below the 40th percentile. The upper and lower Colorado River basins are near to slightly above average. Unfortunately, the long-term temperature pattern remains unchanged, with all areas of the state above the 77th percentile, with the hottest temperatures in Gila County and the southeast climate division, both still above the 96th percentile.