State Precipitation & Temperature Update for Arizona

Conditions through July 2006

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. Values of -99 and grey shading indicate missing data. When the data are available, this product will be updated. Current update is 08/25/2006.

 


Precipitation Percentiles by Watershed (through July 2006)

 

Temperature Percentiles by Climate Division (through July 2006)


SHORT TERM CONDITIONS: 1-6 MONTHS

The month of July was characterized by average or above average precipitation across the entire state, except the Bill Williams watershed in east central Arizona. The San Pedro watershed had the highest July precipitation in 36 years. It should be noted that the Willcox Playa only had 1 of 3 stations reporting for July. July was not quite as hot as June, but all climate divisions except CD1 in the north and CD7 in the southeast were above the 90% percentile. The Virgin and upper Colorado watersheds in the North, the Lower Gila in the Southwest and the White Water Draw in the Southeast had nearly normal precipitation for the 3 month period from May through July, while the eastern and central watersheds had above normal precipitation for the past 3 months. The Bill Williams and Agua Fria were the driest watersheds, but the lower Colorado was above the 80th percentile. These high rainfall percentiles were accompanied by temperatures above the 95th percentile across the southern and western climate division. Even the northwest and north central climate divisions had temperatures above the 85th percentile for the 3 month period. The impact of the extremely dry winter is still apparent in the precipitation percentiles for the past 6-month period, with all watersheds except the San Pedro and Santa Cruz below the 50th percentile. Those two were raised to the 83rd and 61st percentiles, respectively, as a result of the extremely wet July. The wetness of July provides significant drought relief that is apparent up through the 24 month period for the San Pedro watershed.. Temperatures for the 6-month period have been above the 75th percentile everywhere across the state.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

55.71

CD1

85.71%

Upper Colorado

75.00

CD2

90.18%

Little Colorado

88.89

CD3

90.18%

Verde

75.00

CD4

93.75%

Bill Williams

38.89

CD5

95.54%

Agua Fria

58.33

CD6

91.96%

Lower Gila

50.00

CD7

78.57%

Salt

83.33

 

Lower Colorado

77.78

 

Upper Gila

77.78

 

Santa Cruz

91.67

 

San Pedro

100.00

 

Willcox Playa

63.89

 

San Simon

75.00

 

White Water Draw

57.14

 

JULY 2006: 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

54.29

CD1

91.96%

Upper Colorado

55.56

CD2

98.21%

Little Colorado

80.56

CD3

93.75%

Verde

72.22

CD4

95.54%

Bill Williams

38.89

CD5

98.21%

Agua Fria

38.89

CD6

98.21%

Lower Gila

58.33

CD7

96.43%

Salt

72.22

 

Lower Colorado

77.78

 

Upper Gila

66.67

 

Santa Cruz

91.67

 

San Pedro

100.00

 

Willcox Playa

58.33

 

San Simon

75.00

 

White Water Draw

57.14

 

MAY 2006 - JULY 2006 (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

48.57

CD1

79.46%

Upper Colorado

25.00

CD2

94.64%

Little Colorado

44.44

CD3

91.96%

Verde

38.89

CD4

93.75%

Bill Williams

11.11

CD5

88.39%

Agua Fria

16.67

CD6

94.64%

Lower Gila

36.11

CD7

92.86%

Salt

38.89

 

Lower Colorado

36.11

 

Upper Gila

27.78

 

Santa Cruz

61.11

 

San Pedro

83.33

 

Willcox Playa

22.86

 

San Simon

36.11

 

White Water Draw

20.00

 

FEBRUARY 2005 JULY 2006 (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 intermediate time periods of 1- and 2-years show the importance of the historical context of drought. The 1-year period precipitation has been below the 15th percentile for all watersheds except the Virgin, lower Colorado, San Pedro, and White Water Draw. The corresponding temperatures for the 1-year period have been extremely high, above the 85th percentile everywhere except the northeast corner of the state, which is above the 75th percentile.

 

In contrast, the 2-year period shows very little evidence of dryness across the western and west central portions of the state, with precipitation totals above normal. However, the Little Colorado and the southeastern watersheds show precipitation totals below the 35th percentile, with the driest watersheds being the San Pedro and Willcox Playa. This 2-year period still includes the extremely wet winter of 2005 with the extremely dry winter of 2006. Except for climate divisions 1 and 5 along the lower Colorado River, temperatures for the 2-year period were all at or above the 80th percentile.

 


 


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

53.12

CD1

77.48%

Upper Colorado

11.43

CD2

90.99%

Little Colorado

14.29

CD3

90.09%

Verde

11.43

CD4

93.69%

Bill Williams

14.29

CD5

85.59%

Agua Fria

5.71

CD6

94.59%

Lower Gila

11.43

CD7

95.50%

Salt

8.57

 

Lower Colorado

31.43

 

Upper Gila

8.57

 

Santa Cruz

14.29

 

San Pedro

34.29

 

Willcox Playa

14.71

 

San Simon

5.71

 

White Water Draw

22.86

 

AUGUST 2005 JULY 2006 (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

96.88

CD1

72.73%

Upper Colorado

85.29

CD2

88.18%

Little Colorado

38.24

CD3

86.36%

Verde

67.65

CD4

90.91%

Bill Williams

70.59

CD5

78.18%

Agua Fria

61.76

CD6

88.18%

Lower Gila

64.71

CD7

93.64%

Salt

47.06

 

Lower Colorado

91.18

 

Upper Gila

35.29

 

Santa Cruz

17.65

 

San Pedro

32.35

 

Willcox Playa

14.71

 

San Simon

26.47

 

White Water Draw

26.47

 

AUGUST 2004 JULY 2006 (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 pattern of precipitation rankings for the longer-term 3-year period across the state is similar to that of the 2-year period, but includes another very dry winter from 2003-2004. Again, the western and northern watershed precipitation totals were at or above average, the central watersheds were at or slight below normal, and the southeastern watersheds were well below average. The entire state was above the 75th percentile for temperature, and the 3-year period was among the warmest on record in CD 7 in the southeast areas of the state.

 

The length of the current drought and warming is more evident when looking at the longer 4-year period. The northern and western watersheds have had near or above normal precipitation during the 4-year period, while the eastern and southeastern watersheds have received precipitation well below the 25th percentile. Along with the dryness has been excessive heat, particularly in the southeast. Climate divisions 3, 4, 6, and 7 in the south and south central areas have been above the 98th percentile in the 4-year period, with division 7 still having the hottest 4-year period on record.

 


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

90.62

CD1

77.06%

Upper Colorado

75.76

CD2

93.58%

Little Colorado

30.30

CD3

92.66%

Verde

54.55

CD4

96.33%

Bill Williams

63.64

CD5

88.99%

Agua Fria

36.36

CD6

95.41%

Lower Gila

60.61

CD7

99.08%

Salt

36.36

 

Lower Colorado

75.76

 

Upper Gila

18.18

 

Santa Cruz

12.12

 

San Pedro

21.21

 

Willcox Playa

12.12

 

San Simon

21.21

 

White Water Draw

27.27

 

AUGUST 2003 JULY 2006 (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

79.63%

Upper Colorado

65.62

CD2

90.74%

Little Colorado

18.75

CD3

96.30%

Verde

43.75

CD4

97.22%

Bill Williams

46.88

CD5

91.67%

Agua Fria

28.12

CD6

97.22%

Lower Gila

50.00

CD7

100.00%

Salt

25.00

 

Lower Colorado

75.00

 

Upper Gila

18.75

 

Santa Cruz

15.62

 

San Pedro

9.38

 

Willcox Playa

6.25

 

San Simon

21.88

 

White Water Draw

25.00

 

AUGUST 2002 JULY 2006 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 


August 2006 Arizona Drought Update based on Precipitation (data through July 2006)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods. This practice of categorizing the drought in terms of precipitation only will be discontinued as the long term impacts of drought in Arizona are also dependent on stream-flow, soil moisture and temperature, which are not considered here.

 

SUMMARY

The arrival of the above average monsoon rainfall has brought relief from the recent dry conditions that have existed since March across most of the state. Although the 1 month rainfall does not end the drought, it improves the rangeland conditions and provides short term relief. The rainfall brought slightly cooler temperatures, although all areas of the state were above the 75th percentile for temperature.

 

Precipitation totals for the past 3- and 6-month periods were significantly improved by the wet July, particularly across the eastern and south central parts of the state. For the 6 month period, the north and northwest watersheds are still well blow average reflecting the dry spring in those watersheds. The warm winter and hot summer have had the greatest effect across the southern and western areas of the state.

 

The dryness over the past 12 months is evident with almost all watersheds below the 15th percentile for precipitation. The biggest change in the 12 month period is the San Pedro, which improved significantly with the wet July. The southeast has had temperatures above the 95th percentile for the 12-month period.

 

The west, north and central watersheds have had near or above average precipitation for the past 24 months, while the eastern and southeast watersheds have seen slightly to well below average precipitation in this period. Temperatures along the western border have been slightly above normal, but southeast and south central Arizona have had temperatures above the 85th percentile.

 

The 36-month precipitation totals are still at or above average for the 5 western watersheds in Arizona. Eastern central Arizona has had near or slightly below average precipitation for the 36-month period. The southeast has had precipitation totals well below normal, accompanied by temperatures among the highest on record.

 

The long-term problematic areas within the state remain the east-central and southeastern regions, where 4-year precipitation totals are between the 15th dan 5th percentile. These dry conditions are exacerbated by temperatures above the 95th percentile across the southeast, above the 85th percentile in the southwest and northeast, and above the 75th percentile in the northwest.