State Precipitation & Temperature Update for Arizona

Conditions through September 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 10/20/2008. The data are preliminary.


 

Precipitation Percentiles by Watershed (through September 2008)

 

Temperature Percentiles by Climate Division (through September 2008)


SHORT TERM CONDITIONS: 1-6 MONTHS

September was much drier than average across northern and southeastern Arizona, and near average on the Gila, Santa Cruz and Lower Colorado watersheds. It was a very dry end to a wet monsoon. Temperatures were near average in the southeast, and above average elsewhere in the state. The three month period shows how wet the monsoon season was, with the southern half of the state above the 75th percentile. The Little Colorado watershed was drier than average for the monsoon season, and the lower Colorado was near average. The wet conditions kept temperatures below average in southeastern Arizona, but the western half of the state was much warmer than average during the monsoon. The six-month period precipitation, from April through September, was also well above average in the southern half of the state and near or below average in the northern half of the state. Six month temperatures were only slightly above average across most of the state, but above the 88th percentile in Maricopa, Pinal, La Paz and Yuma counties.

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

8.33

CD1

82.89

Upper Colorado

28.95

CD2

68.42

Little Colorado

18.42

CD3

70.18

Verde

26.32

CD4

64.04

Bill Williams

21.05

CD5

87.72

Agua Fria

31.58

CD6

92.98

Lower Gila

52.63

CD7

59.65

Salt

28.95

 

Lower Colorado

42.11

 

Upper Gila

52.63

 

Santa Cruz

42.11

 

San Pedro

31.58

 

Willcox Playa

28.95

 

San Simon

39.47

 

White Water Draw

36.84

 

SEPTEMBER 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

13.89

CD1

90.27

Upper Colorado

68.42

CD2

81.58

Little Colorado

39.47

CD3

85.96

Verde

60.53

CD4

69.30

Bill Williams

57.89

CD5

92.98

Agua Fria

50.00

CD6

90.35

Lower Gila

94.74

CD7

38.60

Salt

89.47

 

Lower Colorado

57.89

 

Upper Gila

97.37

 

Santa Cruz

84.21

 

San Pedro

92.11

 

Willcox Playa

86.84

 

San Simon

89.47

 

White Water Draw

75.68

 

JULY 2008 - SEPTEMBER 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

2.78

CD1

73.45

Upper Colorado

55.26

CD2

68.42

Little Colorado

36.84

CD3

78.95

Verde

42.11

CD4

48.25

Bill Williams

52.63

CD5

88.60

Agua Fria

47.37

CD6

90.35

Lower Gila

94.74

CD7

65.79

Salt

81.58

 

Lower Colorado

56.58

 

Upper Gila

92.11

 

Santa Cruz

78.95

 

San Pedro

94.74

 

Willcox Playa

73.68

 

San Simon

89.47

 

White Water Draw

62.16

 

APRIL 2008 SEPTEMBER 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 precipitation was near or above average everywhere except the Virgin River watershed. Seven watersheds were near average, and seven were above the 62nd percentile. The 12 month period is the wettest period of the previous four years, due to the combination of a wet winter and a wet monsoon season. Temperatures remained warmer than average across the state, with the warmest conditions in the south.

 

The 24-month period had one watershed (lower Gila) with above average precipitation, seven watersheds near average, and seven watersheds below average. Temperatures for the 24-month period continue to be above the 75th percentile across the state, and above the 85th percentile in the southern half of Arizona.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

11.43

CD1

72.57

Upper Colorado

62.16

CD2

63.72

Little Colorado

43.24

CD3

78.76

Verde

51.35

CD4

73.01

Bill Williams

40.54

CD5

79.65

Agua Fria

48.65

CD6

86.28

Lower Gila

86.49

CD7

85.84

Salt

75.68

 

Lower Colorado

45.95

 

Upper Gila

72.97

 

Santa Cruz

62.16

 

San Pedro

64.86

 

Willcox Playa

50.00

 

San Simon

83.78

 

White Water Draw

48.65

 

OCTOBER 2008 SEPTEMBER 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

3.03

CD1

75.00

Upper Colorado

55.56

CD2

83.93

Little Colorado

33.33

CD3

86.61

Verde

27.78

CD4

83.04

Bill Williams

19.44

CD5

89.29

Agua Fria

19.44

CD6

94.64

Lower Gila

77.78

CD7

94.64

Salt

52.78

 

Lower Colorado

36.11

 

Upper Gila

58.33

 

Santa Cruz

27.78

 

San Pedro

41.67

 

Willcox Playa

44.44

 

San Simon

52.78

 

White Water Draw

47.22

 

OCTOBER 2007 SEPTEMBER 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 still the driest period statewide, with the southeast watersheds near average, and the northern half of the state well below average for precipitation. Ten watersheds are below the 40th percentile, and six are below the 25th percentile. Temperatures for the three year period were very warm, with six of the seven climate divisions above the 87th percentile. The southeast climate division continues to be the warmest in 112 years.

 

The 48-month period has nine watersheds with near average, three watersheds (San Simon, Santa Cruz, and San Pedro) with below average precipitation, and three watersheds (upper and lower Colorado and lower Gila) with above average precipitation. The driest areas are in southern Arizona, with the Santa Cruz the driest, below the 24th percentile. The 48-month temperatures continue to be well above average, with all climate divisions above the 75th percentile.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

6.06

CD1

78.38

Upper Colorado

28.57

CD2

87.84

Little Colorado

20.00

CD3

89.19

Verde

11.43

CD4

92.79

Bill Williams

8.57

CD5

90.99

Agua Fria

8.57

CD6

98.20

Lower Gila

57.14

CD7

100.00

Salt

28.57

 

Lower Colorado

25.71

 

Upper Gila

45.71

 

Santa Cruz

20.00

 

San Pedro

42.86

 

Willcox Playa

51.43

 

San Simon

28.57

 

White Water Draw

45.71

 

OCTOBER 2006 SEPTEMBER 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

58.06

CD1

75.45

Upper Colorado

73.53

CD2

89.09

Little Colorado

44.12

CD3

88.18

Verde

55.88

CD4

93.64

Bill Williams

47.06

CD5

85.45

Agua Fria

44.12

CD6

97.27

Lower Gila

79.41

CD7

100.00

Salt

50.00

 

Lower Colorado

82.35

 

Upper Gila

47.06

 

Santa Cruz

23.53

 

San Pedro

38.24

 

Willcox Playa

44.12

 

San Simon

32.35

 

White Water Draw

50.00

 

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

 

October 2008 Arizona Drought Update (based on precipitation data through September 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

September was much drier than average across northern and southeastern Arizona, and near average on the Gila, Santa Cruz and Lower Colorado watersheds. It was a very dry end to a wet monsoon. Temperatures were near average in the southeast, and above average elsewhere in the state.

 

The 3-month period shows how wet the monsoon season was, with the southern half of the state above the 75th percentile. The Little Colorado watershed was drier than average for the monsoon season, and the lower Colorado was near average. The wet conditions kept temperatures below average in southeastern Arizona, but the western half of the state was much warmer than average during the monsoon.

 

The 6-month period precipitation, from April through September, was also well above average in the southern half of the state and near or below average in the northern half of the state. Six month temperatures were only slightly above average across most of the state, but above the 88th percentile in Maricopa, Pinal, La Paz and Yuma counties.

 

The 12-month period precipitation was near or above average everywhere except the Virgin River watershed. Seven watersheds were near average, and seven were above the 62nd percentile. The 12 month period is the wettest period of the previous four years, due to the combination of a wet winter and a wet monsoon season. Temperatures remained warmer than average across the state, with the warmest conditions in the south.

 

The 24-month period had one watershed (lower Gila) with above average precipitation, seven watersheds near average, and seven watersheds below average. Temperatures for the 24-month period continue to be above the 75th percentile across the state, and above the 85th percentile in the southern half of Arizona.

 

The 36-month period is still the driest period statewide, with the southeast watersheds near average, and the northern half of the state well below average for precipitation. Ten watersheds are below the 40th percentile, and six are below the 25th percentile. Temperatures for the three year period were very warm, with six of the seven climate divisions above the 87th percentile. The southeast climate division continues to be the warmest in 112 years.

 

The 48-month period has nine watersheds with near average, three watersheds (San Simon, Santa Cruz, and San Pedro) with below average precipitation, and three watersheds (upper and lower Colorado and lower Gila) with above average precipitation. The driest areas are in southern Arizona, with the Santa Cruz the driest, below the 24th percentile. The 48-month temperatures continue to be well above average, with all climate divisions above the 75th percentile.