State Precipitation & Temperature Update for Arizona

Conditions through June 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 07/21/2008. The data are preliminary.


 

Precipitation Percentiles by Watershed (through June 2008)

 

Temperature Percentiles by Climate Division (through June 2008)


SHORT TERM CONDITIONS: 1-6 MONTHS

June is normally dry statewide, unless the monsoon activity begins early. This year the rainfall began early in southern Arizona, with the lower Gila, Santa Cruz and San Simon watersheds all above the 80th percentile. The Aga Fria and Salt River watersheds were near average, but the rest of the watersheds were below average, between the 18th and 40th percentiles. Temperatures were up significantly since last month, with the northern half of the state between the 77th and 85th percentiles, and the southern half of the state between the 92nd and 94th percentiles. The three-month period of April through June was drier than average in the northern half of the state, and near- or above-average in the southern half of the state. The notable dry exceptions in the southeast are the Willcox and Whitewater Draw watersheds, which remain below the 30th percentile. There is definite short-term improvement, as last month the three month interval was the driest of all the intervals, with 8 watersheds below the 15th percentile, and 12 watersheds below the 25th percentile. The three-month temperatures continue to be near- or slightly above-average. The six-month period precipitation, from January through June, was near average in the central watersheds, above average in the Salt and Upper Colorado watersheds, and below average in the southeast, with the Willcox Playa and Whitewater Draw still below the 18th percentile. Temperatures were near average in the northeast and Yavapai County, slightly above average along the lower Colorado River, and well above average in the southeast.

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

45.95

CD1

84.65

Upper Colorado

36.84

CD2

79.82

Little Colorado

36.84

CD3

82.89

Verde

34.21

CD4

77.63

Bill Williams

18.42

CD5

92.98

Agua Fria

42.11

CD6

93.86

Lower Gila

92.11

CD7

92.11

Salt

55.26

 

Lower Colorado

30.26

 

Upper Gila

26.32

 

Santa Cruz

86.84

 

San Pedro

65.79

 

Willcox Playa

23.68

 

San Simon

84.21

 

White Water Draw

26.32

 

JUNE 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

8.11

CD1

73.45

Upper Colorado

26.32

CD2

52.63

Little Colorado

36.84

CD3

57.46

Verde

23.68

CD4

71.05

Bill Williams

28.95

CD5

73.68

Agua Fria

28.95

CD6

70.18

Lower Gila

81.58

CD7

70.61

Salt

63.16

 

Lower Colorado

84.21

 

Upper Gila

47.37

 

Santa Cruz

47.37

 

San Pedro

52.63

 

Willcox Playa

28.95

 

San Simon

47.37

 

White Water Draw

28.95

 

APRIL 2008 - JUNE 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

16.67

CD1

66.37

Upper Colorado

68.42

CD2

44.74

Little Colorado

51.35

CD3

57.89

Verde

44.74

CD4

67.54

Bill Williams

52.63

CD5

70.18

Agua Fria

44.74

CD6

69.30

Lower Gila

57.89

CD7

79.82

Salt

65.79

 

Lower Colorado

52.63

 

Upper Gila

31.58

 

Santa Cruz

28.95

 

San Pedro

26.32

 

Willcox Playa

17.57

 

San Simon

44.74

 

White Water Draw

8.11

 

JANUARY 2008 JUNE 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 above-average precipitation in five watersheds in the northeast and southwest parts of the state, near-average precipitation in six watersheds in central and southern Arizona, and below average precipitation in four watersheds in the southeast and northwest corners of the state. Temperatures were above the 73rd percentile everywhere, with the warmest temperatures in the south and southeast climate divisions.

 

The 24-month period has seven watersheds near average for precipitation in the eastern half of the state, with two watersheds, the lower Gila and Willcox Playa, above average. Six watersheds are below average, with three between the 30th and 39th percentiles, and 3 below the 22nd percentile, all in the western half of Arizona. The 24-month interval shows much improvement as the dry months of 2006 are replaced by the wetter months of 2008. Temperatures for the 24-month are all below the 95th percentile, but are all above the 73rd percentile. The coolest areas are the northern climate divisions.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

5.71

CD1

73.45

Upper Colorado

75.68

CD2

75.22

Little Colorado

70.27

CD3

77.88

Verde

64.86

CD4

86.28

Bill Williams

45.95

CD5

79.65

Agua Fria

51.35

CD6

87.61

Lower Gila

72.97

CD7

92.04

Salt

72.97

 

Lower Colorado

59.46

 

Upper Gila

43.24

 

Santa Cruz

40.54

 

San Pedro

32.43

 

Willcox Playa

27.78

 

San Simon

54.05

 

White Water Draw

27.78

 

JULY 2008 JUNE 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

2.94

CD1

73.21

Upper Colorado

47.22

CD2

78.57

Little Colorado

58.33

CD3

85.71

Verde

30.56

CD4

85.71

Bill Williams

16.67

CD5

87.50

Agua Fria

22.22

CD6

89.29

Lower Gila

61.11

CD7

94.64

Salt

55.56

 

Lower Colorado

38.89

 

Upper Gila

52.78

 

Santa Cruz

41.67

 

San Pedro

52.78

 

Willcox Playa

61.11

 

San Simon

36.11

 

White Water Draw

58.33

 

JULY 2007 JUNE 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 continues to be the driest long-term period, with five central and southern watersheds below the 12th percentile. Nine watersheds remain below the 25th percentile, and all are below the 35th percentile. For temperature, the two southeast climate divisions remain above the 95th percentile while all the others are between the 76th and 93rd percentiles. Climate division 7 had the hottest 36-month period on record.

 

The 48-month period includes the wet winter of 2005 and is the wettest of the three long-term periods (24-, 36-, and 48-month). However, a comparison of the 36- and 48-month maps shows that the precipitation distribution was not uniform. Even though 2005 was wet in the northern watersheds, it was very dry in the southeast, as were the 36- and 12-month periods. Only four watersheds are above the 60th percentile, while six watersheds are below the 40th percentile for the long-term. Again all climate divisions are above the 75th percentile for temperature, and the southeastern climate division is the hottest, but not quite the hottest on record. It is not a coincidence that the hottest climate divisions match up with the driest watersheds, and the coolest area match up with the wettest watersheds. The presence of cold fronts and cloudy conditions associated with precipitation tend to hold temperatures down. Unfortunately when temperatures climb due to clear skies and the absence of frontal systems, the higher temperatures increase the demand for soil moisture in evaporation and plant transpiration, worsening the impacts of drought on rangeland vegetation.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

9.09

CD1

76.58

Upper Colorado

31.43

CD2

88.29

Little Colorado

28.57

CD3

90.09

Verde

11.43

CD4

92.79

Bill Williams

5.71

CD5

87.39

Agua Fria

5.71

CD6

95.50

Lower Gila

28.57

CD7

100.00

Salt

20.00

 

Lower Colorado

34.29

 

Upper Gila

17.14

 

Santa Cruz

11.43

 

San Pedro

20.00

 

Willcox Playa

28.57

 

San Simon

8.57

 

White Water Draw

34.29

 

JULY 2006 JUNE 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

43.75

CD1

75.45

Upper Colorado

67.65

CD2

90.00

Little Colorado

41.18

CD3

86.36

Verde

61.76

CD4

94.55

Bill Williams

47.06

CD5

84.55

Agua Fria

41.18

CD6

90.00

Lower Gila

64.71

CD7

99.09

Salt

44.12

 

Lower Colorado

76.47

 

Upper Gila

35.29

 

Santa Cruz

11.76

 

San Pedro

11.76

 

Willcox Playa

35.29

 

San Simon

20.59

 

White Water Draw

38.24

 

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

 

July 2008 Arizona Drought Update (based on precipitation data through June 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

June is normally dry statewide, unless the monsoon activity begins early. This year the rainfall began early in southern Arizona, with the lower Gila, Santa Cruz and San Simon watersheds all above the 80th percentile. The Aga Fria and Salt River watersheds were near average, but the rest of the watersheds were below average, between the 18th and 40th percentiles. Temperatures were up significantly since last month, with the northern half of the state between the 77th and 85th percentiles, and the southern half of the state between the 92nd and 94th percentiles.

 

The 3-month period of April through June was drier than average in the northern half of the state, and near- or above-average in the southern half of the state. The notable dry exceptions in the southeast are the Willcox and Whitewater Draw watersheds, which remain below the 30th percentile. There is definite short-term improvement, as last month the three month interval was the driest of all the intervals, with 8 watersheds below the 15th percentile, and 12 watersheds below the 25th percentile. The three-month temperatures continue to be near- or slightly above-average.

 

The 6-month period precipitation, from January through June, was near average in the central watersheds, above average in the Salt and Upper Colorado watersheds, and below average in the southeast, with the Willcox Playa and Whitewater Draw still below the 18th percentile. Temperatures were near average in the northeast and Yavapai County, slightly above average along the lower Colorado River, and well above average in the southeast.

 

The 12-month period had above-average precipitation in five watersheds in the northeast and southwest parts of the state, near-average precipitation in six watersheds in central and southern Arizona, and below average precipitation in four watersheds in the southeast and northwest corners of the state. Temperatures were above the 73rd percentile everywhere, with the warmest temperatures in the south and southeast climate divisions.

 

The 24-month period has seven watersheds near average for precipitation in the eastern half of the state, with two watersheds, the lower Gila and Willcox Playa, above average. Six watersheds are below average, with three between the 30th and 39th percentiles, and three below the 22nd percentile, all in the western half of Arizona. The 24-month interval shows much improvement as the dry months of 2006 are replaced by the wetter months of 2008. Temperatures for the 24-month period are all below the 95th percentile, but are all above the 73rd percentile. The coolest areas are the northern climate divisions.

 

The 36-month period continues to be the driest long-term period, with five central and southern watersheds below the 12th percentile. Nine watersheds remain below the 25th percentile, and all are below the 35th percentile. For temperature, the two southeast climate divisions remain above the 95th percentile while all the others are between the 76th and 93rd percentiles. Climate division 7 had the hottest 36-month period on record.

 

The 48-month period includes the wet winter of 2005 and is the wettest of the three long-term periods (24-, 36-, and 48-month). However, a comparison of the 36- and 48-month maps shows that the precipitation distribution was not uniform. Even though 2005 was wet in the northern watersheds, it was very dry in the southeast, as were the 36- and 12-month periods. Only four watersheds are above the 60th percentile, while six watersheds are below the 40th percentile for the long-term. Again all climate divisions are above the 75th percentile for temperature, and the southeastern climate division is the hottest, but not quite the hottest on record. It is not a coincidence that the hottest climate divisions match up with the driest watersheds, and the coolest area match up with the wettest watersheds. The presence of cold fronts and cloudy conditions associated with precipitation tend to hold temperatures down. Unfortunately when temperatures climb due to clear skies and the absence of frontal systems, the higher temperatures increase the demand for soil moisture in evaporation and plant transpiration, worsening the impacts of drought on rangeland vegetation.