State Precipitation & Temperature Update for Arizona

Conditions through May 2008

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 06/23/2008. The data are preliminary.


 

Precipitation Percentiles by Watershed (through May 2008)

 

Temperature Percentiles by Climate Division (through May 2008)


SHORT TERM CONDITIONS: 1-6 MONTHS

May is normally very dry statewide, but this year it was exceptionally wet in many locations, as three wet low pressure systems moved across the state. Some of the higher elevations even had snow. Precipitation was above the 52nd percentile for all watersheds except the Virgin in NW Arizona. The wettest watershed was the Little Colorado, at the 86th percentile. As a result of the storm systems, which brought unseasonably cold air, all climate divisions except the NW had temperatures near or below average for the month. The three-month period of March through May was drier than average, since both March and April were very dry across the state. The lower Colorado and lower Gila watersheds were the only watersheds above the 21st percentile for precipitation. Central and southeastern Arizona were especially dry, below the 15th percentile. The three month temperatures were near or slightly above average as numerous cold fronts passed through the state, keeping temperatures down. The 6-month period precipitation, from December through May, was near average in the southeast and above average in the rest of the state, due to the wet months of December through February. Ten watersheds were between the 62nd and 79th percentiles. The driest watersheds, in the southeast, should start to recover as the monsoon develops. Temperatures were near average in the southern and western parts of the state, and cooler than average on the Colorado Plateau. Gila County was slightly warmer than average.

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

31.58

CD1

62.72

Upper Colorado

63.16

CD2

29.39

Little Colorado

86.84

CD3

28.07

Verde

85.53

CD4

50.88

Bill Williams

81.58

CD5

55.26

Agua Fria

84.21

CD6

45.18

Lower Gila

94.74

CD7

44.74

Salt

94.74

 

Lower Colorado

92.11

 

Upper Gila

89.47

 

Santa Cruz

52.63

 

San Pedro

73.68

 

Willcox Playa

81.58

 

San Simon

57.89

 

White Water Draw

76.32

 

MAY 2008: 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

5.26

CD1

69.30

Upper Colorado

21.05

CD2

43.86

Little Colorado

15.79

CD3

53.51

Verde

10.53

CD4

70.18

Bill Williams

13.16

CD5

65.35

Agua Fria

7.89

CD6

66.67

Lower Gila

31.58

CD7

60.09

Salt

15.79

 

Lower Colorado

50.00

 

Upper Gila

13.16

 

Santa Cruz

10.53

 

San Pedro

13.16

 

Willcox Playa

18.42

 

San Simon

13.16

 

White Water Draw

21.05

 

MARCH 2008 - MAY 2008 (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

50.00

CD1

53.51

Upper Colorado

75.68

CD2

30.70

Little Colorado

77.78

CD3

39.47

Verde

63.89

CD4

62.28

Bill Williams

64.86

CD5

46.93

Agua Fria

67.57

CD6

46.93

Lower Gila

75.68

CD7

52.19

Salt

78.38

 

Lower Colorado

64.86

 

Upper Gila

62.16

 

Santa Cruz

59.46

 

San Pedro

48.57

 

Willcox Playa

47.22

 

San Simon

72.97

 

White Water Draw

50.00

 

DECEMBER 2008 MAY 2008 (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 had near- or below-average precipitation in 5 watersheds in west central and southeastern Arizona, and above-average precipitation on the Colorado Plateau and in southwestern Arizona on the lower Gila River watershed. The cooler temperatures in May brought the twelve month temperature average down slightly on the Colorado Plateau, and in west central and southwestern Arizona. However, temperatures are still high, with all climate divisions above the 70th percentile.

 

The 24-month period was slightly wetter than last month, with three watersheds now above average for the 24-month period. The lower Gila, Willcox Playa and Whitewater Draw have moved up to the 61st percentile. The rest of the state is near or slightly below average, with the Bill Williams and Agua Fria the driest, below the25th percentile. Temperatures for the 24-month period cooled slightly so that all climate divisions are below the 93rd percentile and climate division 1 in the NW is at the 75th percentile.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

5.71

CD1

70.80

Upper Colorado

70.27

CD2

71.68

Little Colorado

70.27

CD3

82.30

Verde

62.16

CD4

89.38

Bill Williams

45.95

CD5

79.65

Agua Fria

51.35

CD6

85.84

Lower Gila

70.27

CD7

88.50

Salt

72.97

 

Lower Colorado

59.46

 

Upper Gila

45.95

 

Santa Cruz

37.84

 

San Pedro

37.84

 

Willcox Playa

33.33

 

San Simon

54.05

 

White Water Draw

38.89

 

JUNE 2008 MAY 2008 (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

5.88

CD1

75.00

Upper Colorado

47.22

CD2

79.02

Little Colorado

58.33

CD3

86.61

Verde

33.33

CD4

88.39

Bill Williams

16.67

CD5

87.50

Agua Fria

22.22

CD6

91.07

Lower Gila

61.11

CD7

92.86

Salt

55.56

 

Lower Colorado

38.89

 

Upper Gila

52.78

 

Santa Cruz

36.11

 

San Pedro

52.78

 

Willcox Playa

61.11

 

San Simon

38.89

 

White Water Draw

61.11

 

JUNE 2007 MAY 2008 (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 is the driest long-term period, with most of the southeast and central watersheds at or below the 20th percentile. All watersheds remain below the 32nd percentile, and seven watersheds are below the 15th percentile. For temperature, the southeast climate divisions remain above the 95th percentile and even the coolest climate division, in the northwest, is still above the 75th percentile.

 

The 48-month period had dry conditions in the southeast, and near average conditions in central Arizona, and wet conditions in central and western Arizona. The 48 month period includes the winters of 2004-05, 2005-06, 2006-07, and 2007-08 and the summers of 2004 2007. In central and northern Arizona watersheds, 2005 was the wettest of the past four years, while in the driest southeast watersheds, 2004 was the wettest year. All climate divisions are above the 74th percentile for temperature, but the southwest climate division has dropped below the 85th percentile.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

9.09

CD1

75.23

Upper Colorado

31.43

CD2

88.29

Little Colorado

28.57

CD3

89.19

Verde

11.43

CD4

92.79

Bill Williams

5.71

CD5

90.09

Agua Fria

5.71

CD6

95.50

Lower Gila

28.57

CD7

100.00

Salt

20.00

 

Lower Colorado

31.43

 

Upper Gila

14.29

 

Santa Cruz

8.57

 

San Pedro

17.14

 

Willcox Playa

31.43

 

San Simon

5.71

 

White Water Draw

31.43

 

JUNE 2006 MAY 2008 (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

45.16

CD1

74.55

Upper Colorado

70.59

CD2

88.18

Little Colorado

38.24

CD3

86.36

Verde

58.82

CD4

94.55

Bill Williams

47.06

CD5

83.64

Agua Fria

41.18

CD6

90.91

Lower Gila

63.24

CD7

98.18

Salt

44.12

 

Lower Colorado

76.47

 

Upper Gila

32.35

 

Santa Cruz

8.82

 

San Pedro

11.76

 

Willcox Playa

35.29

 

San Simon

17.65

 

White Water Draw

41.18

 

JUNE 2005 MAY 2008 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

June 2008 Arizona Drought Update (based on precipitation data through May 2008)

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

 

SUMMARY

May is normally very dry statewide, but this year it was exceptionally wet in many locations, as three wet low pressure systems moved across the state. Some of the higher elevations even had snow. Precipitation was above the 52nd percentile for all watersheds except the Virgin in NW Arizona. The wettest watershed was the Little Colorado, at the 86th percentile. As a result of the storm systems, which brought unseasonably cold air, all climate divisions except the NW had temperatures near or below average for the month.

 

The 3-month period of March through May was drier than average, since both March and April were very dry across the state. The lower Colorado and lower Gila watersheds were the only watersheds above the 21st percentile for precipitation. Central and southeastern Arizona were especially dry, below the 15th percentile. The three month temperatures were near or slightly above average as numerous cold fronts passed through the state, keeping temperatures down.

 

The 6-month period precipitation, from December through May, was near average in the southeast and above average in the rest of the state, due to the wet months of December through February. Ten watersheds were between the 62nd and 79th percentiles. The driest watersheds, in the southeast, should start to recover as the monsoon develops. Temperatures were near average in the southern and western parts of the state, and cooler than average on the Colorado Plateau. Gila County was slightly warmer than average.

 

The 12-month period had near- or below-average precipitation in 5 watersheds in west central and southeastern Arizona, and above-average precipitation on the Colorado Plateau and in southwestern Arizona on the lower Gila River watershed. The cooler temperatures in May brought the twelve month temperature average down slightly on the Colorado Plateau, and in west central and southwestern Arizona. However, temperatures are still high, with all climate divisions above the 70th percentile.

 

The 24-month period was slightly wetter than last month, with three watersheds now above average for the 24-month period. The lower Gila, Willcox Playa and Whitewater Draw have moved up to the 61st percentile. The rest of the state is near or slightly below average, with the Bill Williams and Agua Fria the driest, below the25th percentile. Temperatures for the 24-month period cooled slightly so that all climate divisions are below the 93rd percentile and climate division 1 in the NW is at the 75th percentile.

 

The 36-month period is the driest long-term period, with most of the southeast and central watersheds at or below the 20th percentile. All watersheds remain below the 32nd percentile, and seven watersheds are below the 15th percentile. For temperature, the southeast climate divisions remain above the 95th percentile and even the coolest climate division, in the northwest, is still above the 75th percentile.

 

The 48-month period had dry conditions in the southeast, and near average conditions in central Arizona, and wet conditions in central and western Arizona. The 48 month period includes the winters of 2004-05, 2005-06, 2006-07, and 2007-08 and the summers of 2004 2007. In central and northern Arizona watersheds, 2005 was the wettest of the past four years, while in the driest southeast watersheds, 2004 was the wettest year. All climate divisions are above the 74th percentile for temperature, but the southwest climate division has dropped below the 85th percentile.