State Precipitation & Temperature Update for Arizona

Conditions through January 2009

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 03/16/2009. The data are preliminary.


Precipitation Percentiles by Watershed (through January 2009)

 

Temperature Percentiles by Climate Division (through January 2009)


SHORT TERM CONDITIONS: 1-6 MONTHS

January was unusually dry across the entire state, with the driest conditions in the Bill Williams and lower Colorado watersheds. Three moderate winter storms moved through the state between the 7th and the 17th of the month, but precipitation totals in northern and southern Arizona were generally less than an inch, except at the higher elevations. Central Arizona had snow and rain amounts between 1 and 3 inches. Temperatures were above the 95th percentile in Maricopa, Pinal, Yuma and La Paz counties. The three-month period of December through January was much wetter than average for all but the southeastern third of the state. The two driest watersheds, Santa Cruz and Willcox Playa were below the 36th percentile. Temperatures for the three month period were well above average everywhere, with all counties, except Gila, above the 81st percentile. The six-month period precipitation is much less homogeneously distributed. The northern watersheds, had near average precipitation, although the Virgin River watershed was very dry at the 14th percentile, and the Little Colorado River watershed was just below the 30th percentile. The southeastern watersheds were drier than average, while the Salt, lower Gila and San Simon watersheds in central and southwestern Arizona were slightly wetter than average during the last six months. Again, only Gila County had near average temperatures for the past six months. Maricopa, Pinal, La Paz and Yuma County had very warm temperatures, above the 97th percentile.

Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

39.47

CD1

92.17

Upper Colorado

33.33

CD2

84.35

Little Colorado

39.47

CD3

92.17

Verde

28.21

CD4

92.17

Bill Williams

23.08

CD5

95.65

Agua Fria

28.21

CD6

95.65

Lower Gila

33.33

CD7

93.91

Salt

43.59

 

Lower Colorado

12.82

 

Upper Gila

38.46

 

Santa Cruz

38.46

 

San Pedro

35.90

 

Willcox Playa

38.46

 

San Simon

38.46

 

White Water Draw

36.84

 

JANUARY 2009: 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

55.56

CD1

81.74

Upper Colorado

76.32

CD2

85.22

Little Colorado

70.27

CD3

83.48

Verde

70.27

CD4

69.13

Bill Williams

65.79

CD5

93.04

Agua Fria

71.05

CD6

91.30

Lower Gila

71.05

CD7

84.35

Salt

78.95

 

Lower Colorado

78.95

 

Upper Gila

50.00

 

Santa Cruz

36.84

 

San Pedro

47.22

 

Willcox Playa

40.54

 

San Simon

52.63

 

White Water Draw

35.14

 

NOVEMBER 2008 - JANUARY 2009 (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

14.29

CD1

81.74

Upper Colorado

57.89

CD2

81.74

Little Colorado

29.73

CD3

85.22

Verde

48.65

CD4

51.30

Bill Williams

52.63

CD5

97.39

Agua Fria

42.11

CD6

98.26

Lower Gila

60.53

CD7

72.17

Salt

71.05

 

Lower Colorado

55.26

 

Upper Gila

42.11

 

Santa Cruz

34.21

 

San Pedro

36.11

 

Willcox Playa

18.92

 

San Simon

60.53

 

White Water Draw

29.73

 

AUGUST 2008 JANUARY 2009 (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 very mixed across the state, just like the six month period. Northern Arizona was generally drier than average, while southern Arizona was wetter in the west and drier than average in the east. This reflects the dry fall and winter in southern Arizona, as the summer was very wet in the southeastern watersheds. Gila County continues to be the only area with near average temperatures for the previous year. The northern half of the state was slightly warmer than average, while the southern half of the state was much warmer than average.

 

The 24 month period is the wettest long-term period, but is inconsistent from watershed to watershed. Seven watersheds in central and southern Arizona had slightly below average precipitation over the last two years, while five watersheds in north, east central and southwest Arizona were wetter than average. Three watersheds had near average precipitation. Temperatures in the past two years have been well above average in all areas of the state, with the warmest temperatures in Maricopa and Pinal counties.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

5.56

CD1

73.68

Upper Colorado

57.89

CD2

71.93

Little Colorado

23.68

CD3

82.46

Verde

26.32

CD4

43.86

Bill Williams

31.58

CD5

94.74

Agua Fria

23.68

CD6

98.25

Lower Gila

76.32

CD7

83.77

Salt

71.05

 

Lower Colorado

52.63

 

Upper Gila

55.26

 

Santa Cruz

36.84

 

San Pedro

55.26

 

Willcox Playa

34.21

 

San Simon

60.53

 

White Water Draw

40.54

 

FEBRUARY 2008 JANUARY 2009 (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

2.86

CD1

76.99

Upper Colorado

72.97

CD2

90.27

Little Colorado

48.65

CD3

88.50

Verde

37.84

CD4

82.30

Bill Williams

29.73

CD5

92.92

Agua Fria

32.43

CD6

98.23

Lower Gila

81.08

CD7

94.69

Salt

81.08

 

Lower Colorado

51.35

 

Upper Gila

62.16

 

Santa Cruz

32.43

 

San Pedro

43.24

 

Willcox Playa

37.84

 

San Simon

62.16

 

White Water Draw

35.14

 

FEBRUARY 2007 JANUARY 2009 (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 shows the upper and Little Colorado River watersheds had near average precipitation, while the Bill Williams, Verde and Agua Fria watersheds, also in northern Arizona had much lower than average precipitation. In southern Arizona, the upper and lower Gila, Salt and Willcox watersheds were wetter than average, but the Santa Cruz and lower Colorado were slightly drier than average. Five watersheds across the state were near average for precipitation. Temperatures over the three-year period remain extremely high with only the northwest climate division below the 84th percentile, and the southern climate divisions above the 97th percentile.

 

The 48-month period became the driest period last month, and it continues to be the driest period as the winter of 2008-2009 replaces the winter of 2004-2005. Six watersheds are below the 25th percentile, five watersheds are between the 25th and 40th percentile, and four watersheds are above the 40th percentile. The four-year temperatures continue to be extremely high, with the southern third of the state above the 99th percentile, and the coolest climate division, Mohave County in the northwest, still above the 75th percentile.


Watershed

Precipitation Percentile

Climate Division

Temperature Percentile

Virgin

5.88

CD1

76.79

Upper Colorado

44.44

CD2

88.39

Little Colorado

52.78

CD3

88.39

Verde

25.00

CD4

84.82

Bill Williams

11.11

CD5

91.96

Agua Fria

16.67

CD6

97.32

Lower Gila

69.44

CD7

98.21

Salt

63.89

 

Lower Colorado

33.33

 

Upper Gila

63.89

 

Santa Cruz

27.78

 

San Pedro

58.33

 

Willcox Playa

61.11

 

San Simon

44.44

 

White Water Draw

50.00

 

FEBRUARY 2006 JANUARY 2009 (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

25.00

CD1

75.68

Upper Colorado

48.57

CD2

90.09

Little Colorado

31.43

CD3

87.39

Verde

20.00

CD4

90.99

Bill Williams

8.57

CD5

90.09

Agua Fria

8.57

CD6

99.10

Lower Gila

60.00

CD7

100.00

Salt

54.29

 

Lower Colorado

40.00

 

Upper Gila

42.86

 

Santa Cruz

11.43

 

San Pedro

31.43

 

Willcox Playa

31.43

 

San Simon

14.29

 

White Water Draw

37.14

 

FEBRUARY 2005 JANUARY 2009 (48-month): percentiles of temperature, and precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

 

February 2008 Arizona Drought Update based on precipitation data through January 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

January was unusually dry across the entire state, with the driest conditions in the Bill Williams and lower Colorado watersheds. Three moderate winter storms moved through the state between the 7th and the 17th of the month, but precipitation totals in northern and southern Arizona were generally less than an inch, except at the higher elevations. Central Arizona had snow and rain amounts between 1 and 3 inches. Temperatures were above the 95th percentile in Maricopa, Pinal, Yuma and La Paz counties.

 

The 3-month period of December through January was much wetter than average for all but the southeastern third of the state. The two driest watersheds, Santa Cruz and Willcox Playa were below the 36th percentile. Temperatures for the three month period were well above average everywhere, with all counties, except Gila, above the 81st percentile.

 

The 6-month period precipitation is much less homogeneously distributed. The northern watersheds, had near average precipitation, although the Virgin River watershed was very dry at the 14th percentile, and the Little Colorado River watershed was just below the 30th percentile. The southeastern watersheds were drier than average, while the Salt, lower Gila and San Simon watersheds in central and southwestern Arizona were slightly wetter than average during the last six months. Again, only Gila County had near average temperatures for the past six months. Maricopa, Pinal, La Paz and Yuma County had very warm temperatures, above the 97th percentile.

 

The 12-month period precipitation was very mixed across the state, just like the six month period. Northern Arizona was generally drier than average, while southern Arizona was wetter in the west and drier than average in the east. This reflects the dry fall and winter in southern Arizona, as the summer was very wet in the southeastern watersheds. Gila County continues to be the only area with near average temperatures for the previous year. The northern half of the state was slightly warmer than average, while the southern half of the state was much warmer than average.

 

The 24 month period is the wettest long-term period, but is inconsistent from watershed to watershed. Seven watersheds in central and southern Arizona had slightly below average precipitation over the last two years, while five watersheds in north, east central and southwest Arizona were wetter than average. Three watersheds had near average precipitation. Temperatures in the past two years have been well above average in all areas of the state, with the warmest temperatures in Maricopa and Pinal counties.

 

The 36-month period shows the upper and Little Colorado River watersheds had near average precipitation, while the Bill Williams, Verde and Agua Fria watersheds, also in northern Arizona had much lower than average precipitation. In southern Arizona, the upper and lower Gila, Salt and Willcox watersheds were wetter than average, but the Santa Cruz and lower Colorado were slightly drier than average. Five watersheds across the state were near average for precipitation. Temperatures over the three-year period remain extremely high with only the northwest climate division below the 84th percentile, and the southern climate divisions above the 97th percentile.

 

The 48-month period became the driest period last month, and it continues to be the driest period as the winter of 2008-2009 replaces the winter of 2004-2005. Six watersheds are below the 25th percentile, five watersheds are between the 25th and 40th percentile, and four watersheds are above the 40th percentile. The four-year temperatures continue to be extremely high, with the southern third of the state above the 99th percentile, and the coolest climate division, Mohave County in the northwest, still above the 75th percentile.