State Precipitation & Temperature Update for Arizona

Conditions through September 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. Current update is 10/26/2006.


 

Precipitation Percentiles by Watershed (through September 2006)

 

Temperature Percentiles by Climate Division (through September 2006)


SHORT TERM CONDITIONS: 1-6 MONTHS

September brought above-average rainfall to central and southern Arizona, while the northern third of the state had average or slightly below average rainfall. The southeast and northwest corners of the state again had cooler than normal temperatures for the second month in a row, while the northeast and southwest were near or slightly above average for temperature. For the 3 month period of July through September, reflecting the wet monsoon months, precipitation was well above normal across the state, with the Upper Colorado basin near average. The temperatures ranged from the 25th percentile in the southeast corner to the 90th percentile in the southwest corner of the state. The 6 month period, which drops the wet March and adds the wet September, is still above the 60th percentile for precipitation across the central and southern watersheds. The Upper Colorado and Bill Williams received slightly less than average precipitation. As a result of dropping the cool wet month of March from the 6-month period, the temperatures across the state for the past 6 months are all above the 75th percentile, and most of the southern and western parts of the state were above the 85th temperature percentile.

 

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

64.71

CD1

61.16

Upper Colorado

30.56

CD2

17.41

Little Colorado

50.00

CD3

22.32

Verde

55.56

CD4

12.95

Bill Williams

61.11

CD5

57.14

Agua Fria

72.22

CD6

54.91

Lower Gila

83.33

CD7

25.89

Salt

66.67

 

Lower Colorado

75.00

 

Upper Gila

61.11

 

Santa Cruz

80.56

 

San Pedro

97.22

 

Willcox Playa

91.67

 

San Simon

83.33

 

White Water Draw

91.67

 

SEPTEMBER 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

27.94

CD1

78.13

Upper Colorado

47.22

CD2

41.07

Little Colorado

80.56

CD3

60.71

Verde

75.00

CD4

46.43

Bill Williams

30.56

CD5

88.39

Agua Fria

83.33

CD6

78.13

Lower Gila

66.67

CD7

38.39

Salt

80.56

 

Lower Colorado

66.67

 

Upper Gila

86.11

 

Santa Cruz

86.11

 

San Pedro

100.00

 

Willcox Playa

97.22

 

San Simon

72.22

 

White Water Draw

91.43

 

JULY 2006 - SEPTEMBER 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

29.41

CD1

81.25

Upper Colorado

27.78

CD2

89.29

Little Colorado

63.89

CD3

91.96

Verde

63.89

CD4

86.61

Bill Williams

30.56

CD5

96.43

Agua Fria

66.67

CD6

94.64

Lower Gila

69.44

CD7

100.00

Salt

72.22

 

Lower Colorado

63.89

 

Upper Gila

72.22

 

Santa Cruz

86.11

 

San Pedro

100.00

 

Willcox Playa

91.67

 

San Simon

69.44

 

White Water Draw

91.43

 

APRIL 2005 SEPTEMBER 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 12 month period continues to show the effects of a very dry winter of 2005. All watersheds, except the Willcox Playa and White Water Draw in the southeast and the Lower Colorado in the southwest, remain below the 25th percentile. The replacement of the dry September of 2005 with the wet September of 2006 led to some improvement in the 12-month period, particularly on the Northeast plateau. The corresponding temperatures for the 1-year period remain 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 the eastern half of the state below the 40th percentile for precipitation and the western half above the 60th percentile. The monsoon rainfall improved the southeast areas considerably. The 24-month temperatures remain well above the 75th percentile of most areas, with the southeast climate division at the 99th percentile.

 


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

36.36

CD1

76.58

Upper Colorado

17.14

CD2

90.99

Little Colorado

20.00

CD3

90.99

Verde

17.14

CD4

93.69

Bill Williams

8.57

CD5

90.09

Agua Fria

14.29

CD6

93.69

Lower Gila

14.29

CD7

99.10

Salt

11.43

 

Lower Colorado

28.57

 

Upper Gila

11.43

 

Santa Cruz

22.86

 

San Pedro

54.29

 

Willcox Playa

41.18

 

San Simon

14.29

 

White Water Draw

42.86

 

SEPTEMBER 2005 SEPTEMBER 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

96.77

CD1

72.73

Upper Colorado

82.35

CD2

90.00

Little Colorado

47.06

CD3

86.82

Verde

76.47

CD4

92.73

Bill Williams

73.53

CD5

82.73

Agua Fria

76.47

CD6

91.82

Lower Gila

76.47

CD7

99.09

Salt

50.00

 

Lower Colorado

100.00

 

Upper Gila

41.18

 

Santa Cruz

26.47

 

San Pedro

38.24

 

Willcox Playa

41.18

 

San Simon

23.53

 

White Water Draw

52.94

 

SEPTEMBER 2004 SEPTEMBER 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

There is still little change in the 36 month precipitation rankings since the September update, with the western half of the state remaining near or above-average, while the eastern half of the state is still below average, with the Santa Cruz and San Simon watersheds at the 12th and 21st percentiles, respectively. The entire state is still above the 75th percentile for temperature, but climate division dropped below the 95th percentile this month. Climate divisions 4 and 7 in the southeast remain above the 95th percentile for temperature.

 

The Little Colorado watershed has finally moved above the 25th percentile for precipitation in the 4-year period. There is little change in the other watersheds. The eastern watersheds remain below average while the western watersheds remain near or above normal. Recent months of monsoon moisture have not changed the excessive heat pattern evident over the past 4 years. Temperatures have remained above the 95th percentile in the southeast and south central climate divisions, and above the 75th percentile elsewhere in the state.

 

 


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

93.55

CD1

77.06

Upper Colorado

63.64

CD2

91.28

Little Colorado

27.27

CD3

89.91

Verde

54.55

CD4

96.33

Bill Williams

48.48

CD5

87.16

Agua Fria

48.48

CD6

94.50

Lower Gila

60.61

CD7

99.08

Salt

39.39

 

Lower Colorado

78.79

 

Upper Gila

30.30

 

Santa Cruz

12.12

 

San Pedro

39.39

 

Willcox Playa

39.39

 

San Simon

21.21

 

White Water Draw

54.55

 

SEPTEMBER 2003 SEPTEMBER 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

78.70

Upper Colorado

65.62

CD2

90.74

Little Colorado

15.62

CD3

95.37

Verde

50.00

CD4

98.15

Bill Williams

53.12

CD5

92.59

Agua Fria

40.62

CD6

98.15

Lower Gila

59.38

CD7

100.00

Salt

28.12

 

Lower Colorado

75.00

 

Upper Gila

18.75

 

Santa Cruz

15.62

 

San Pedro

15.62

 

Willcox Playa

9.38

 

San Simon

25.00

 

White Water Draw

28.12

 

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

 

October 2006 Arizona Drought Update based on Precipitation (data through September 2006)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods. The Virgin River watershed has not yet reported precipitation data, and the Santa Cruz watershed has only a few stations reporting so far, so the results are preliminary.

 

SUMMARY

September brought above-average rainfall to central and southern Arizona, while the northern third of the state had average or slightly below average rainfall. The southeast and northwest corners of the state again had cooler than normal temperatures for the second month in a row, while the northeast and southwest were near or slightly above average for temperature.

 

Three-month period As a result of the wet monsoon, precipitation was well above normal across the state, with the Upper Colorado basin near average. The temperatures ranged from the 25th percentile in the southeast corner to the 90th percentile in the southwest corner of the state.

 

Six-month period The central and southern watersheds are still above the 60th percentile for precipitation. The Upper Colorado and Bill Williams received slightly less than average precipitation. As a result of dropping the cool wet month of March from the 6-month period, the temperatures across the state for the past 6 months are all above the 75th percentile, and most of the southern and western parts of the state were above the 85th temperature percentile.

 

Twelve-month period - continues to show the effects of a very dry winter of 2005. All watersheds, except the Willcox Playa and White Water Draw in the southeast and the Lower Colorado in the southwest, remain below the 25th percentile. The replacement of the dry September of 2005 with the wet September of 2006 led to some improvement in the 12-month period, particularly on the Northeast plateau. The corresponding temperatures for the 1-year period remain extremely high, above the 85th percentile everywhere except the northeast corner of the state, which is above the 75th percentile.

 

Two-year period - shows the eastern half of the state below the 40th percentile for precipitation and the western half above the 60th percentile. The monsoon rainfall improved the southeast areas considerably. The 24-month temperatures remain well above the 75th percentile of most areas, with the southeast climate division at the 99th percentile.

 

Three-year period - There is still little change in precipitation percentiles since the September update, with the western half of the state remaining near of above-average, while the eastern half of the state is still below average, with the Santa Cruz and San Simon watersheds at the 12th and 21st percentiles, respectively. The entire state is still above the 75th percentile for temperature, but climate division 6 dropped below the 95th percentile this month. Climate divisions 4 and 7 in the southeast remain above the 95th percentile for temperature.

 

Four-year period - The Little Colorado watershed has finally moved above the 25th percentile for precipitation in the 4-year period. There is little change in the other watersheds. The eastern watersheds remain below average while the western watersheds remain near or above normal. Recent months of monsoon moisture have not changed the excessive heat pattern evident over the past 4 years. Temperatures have remained above the 95th percentile in the southeast and south central climate divisions, and above the 75th percentile elsewhere in the state.