State Precipitation & Temperature Update for Arizona

Conditions through July 2012

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 100^th 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 100^th 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. The percentiles have shifted to reflect the percentile categories used in the National Drought Monitor. Current update is 9/09/2012. The data are preliminary.

Precipitation Percentiles by Watershed (through July 2012)

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Temperature Percentiles by Climate Division (through July 2012)

SHORT TERM CONDITIONS: 1-6 MONTHS

July was much wetter than normal across the northern half of the state and drier than normal in the southeastern watersheds. Temperatures were only slightly warmer than normal statewide, due to the monsoon activity which generally brings cooling. The three month period was also much wetter than normal everywhere except the southeastern watersheds. Three month temperatures were much warmer than average statewide with all counties except Gila, above the 89^th percentile. Six month precipitation was near average in six watersheds, and below average in eight watersheds. Only the Bill Williams watershed was wetter than average. Six month temperatures were above the 86^th percentile everywhere except the Colorado Plateau, though even plateau was above the 77^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	3.66	CD1	81.78
Upper Colorado	92.86	CD2	56.78
Little Colorado	88.10	CD3	69.92
Verde	90.48	CD4	75.85
Bill Williams	95.24	CD5	64.41
Agua Fria	90.48	CD6	78.39
Lower Gila	83.33	CD7	55.93
Salt	88.10
Lower Colorado	90.48
Upper Gila	71.43
Santa Cruz	57.14
San Pedro	83.33
Willcox Playa	50.00
San Simon	20.24
White Water Draw	14.63

July 2012: 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	2.44	CD1	89.74
Upper Colorado	80.95	CD2	89.83
Little Colorado	64.29	CD3	93.22
Verde	78.57	CD4	77.12
Bill Williams	88.10	CD5	93.22
Agua Fria	83.33	CD6	94.07
Lower Gila	83.33	CD7	94.92
Salt	73.81
Lower Colorado	80.95
Upper Gila	61.90
Santa Cruz	61.90
San Pedro	83.33
Willcox Playa	38.10
San Simon	35.71
White Water Draw	17.07

May 2012 - July 2012 (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	2.44	CD1	86.32
Upper Colorado	28.57	CD2	82.20
Little Colorado	33.33	CD3	89.83
Verde	35.71	CD4	77.12
Bill Williams	61.90	CD5	91.53
Agua Fria	47.62	CD6	92.37
Lower Gila	42.86	CD7	94.07
Salt	19.05
Lower Colorado	38.10
Upper Gila	21.43
Santa Cruz	26.19
San Pedro	35.71
Willcox Playa	17.07
San Simon	26.19
White Water Draw	7.32

February 2011 – July 2012 (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 was near or slightly drier than normal with the near average conditions in the southeast watersheds including San Pedro, Santa Cruz and Willcox Playa, and the Little Colorado, Bill Williams and lower Gila. The driest watersheds were the Salt, lower Colorado and San Simon. The wettest watershed was at the 41^st percentile. The twelve month period was also very warm with all counties above the 80^th percentile, and the southern two-thirds of the state above the 85^th percentile.

The 24-month period is still the driest long-term interval after two back-to-back La Niña years. Thirteen watersheds were at or below the 20^th percentile and eight were at or below the 10^th percentile. Only the upper and Little Colorado watersheds had near average precipitation. The 24 month interval is still the warmest long term period with seven southern and southeastern counties above the 95^th percentile. Only Mohave County is below the 70^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	5.26	CD1	80.34
Upper Colorado	26.83	CD2	84.62
Little Colorado	41.46	CD3	89.74
Verde	29.27	CD4	85.04
Bill Williams	39.02	CD5	92.31
Agua Fria	29.27	CD6	93.16
Lower Gila	31.71	CD7	94.87
Salt	19.51
Lower Colorado	17.07
Upper Gila	26.83
Santa Cruz	31.71
San Pedro	31.71
Willcox Playa	32.50
San Simon	17.07
White Water Draw	26.83

August 2011 - July 2012 (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	13.16	CD1	69.83
Upper Colorado	45.00	CD2	78.45
Little Colorado	32.50	CD3	86.21
Verde	17.50	CD4	87.93
Bill Williams	20.00	CD5	87.93
Agua Fria	10.00	CD6	92.24
Lower Gila	10.00	CD7	98.28
Salt	15.00
Lower Colorado	20.00
Upper Gila	5.00
Santa Cruz	2.50
San Pedro	10.00
Willcox Playa	7.50
San Simon	2.50
White Water Draw	7.50

August 2010 – July 2012 (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 has eleven watersheds below the 22^nd percentile. The driest watersheds are in the southeast, though the Verde and Agua Fria are both below the 18^th percentile. The Upper and Little Colorado Basins are above the 43^rd percentile, largely due to the El Niño winter of 2010. Temperatures for the three year period were slightly warmer than average across the northern counties, and much warmer than average over the southern counties.

The 48-month period was very dry over the southern two-thirds of the state with the exceptions of the Salt and lower Gila watersheds which both had near average precipitation. Four watersheds in the southeast were below the 8^th percentile. Eleven counties in the southern half of the state were above the 85^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	21.05	CD1	66.96
Upper Colorado	48.72	CD2	70.43
Little Colorado	43.59	CD3	82.61
Verde	17.95	CD4	80.87
Bill Williams	20.51	CD5	81.74
Agua Fria	15.38	CD6	90.43
Lower Gila	38.46	CD7	93.04
Salt	25.64
Lower Colorado	33.33
Upper Gila	10.26
Santa Cruz	5.13
San Pedro	17.95
Willcox Playa	12.82
San Simon	2.56
White Water Draw	12.82

August 2009 - July 2012 (36-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	8.33	CD1	67.54
Upper Colorado	47.37	CD2	80.70
Little Colorado	28.95	CD3	84.21
Verde	18.42	CD4	80.26
Bill Williams	21.05	CD5	85.09
Agua Fria	13.16	CD6	99.12
Lower Gila	39.47	CD7	92.98
Salt	34.21
Lower Colorado	21.05
Upper Gila	15.79
Santa Cruz	2.63
San Pedro	7.89
Willcox Playa	10.53
San Simon	2.63
White Water Draw	2.63

August 2008- July 2012 (48-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

August 2012 Arizona Drought Update (based on precipitation data through July 2012)

The following summary describes the heat and dryness across the state for the 1-, 3-, 6-, 12-, 24-, 36-, and 48-month periods.

SUMMARY

July was much wetter than normal across the northern half of the state and drier than normal in the southeastern watersheds. Temperatures were only slightly warmer than normal statewide, due to the monsoon activity which generally brings cooling.

The 3-month period was also much wetter than normal everywhere except the southeastern watersheds. Three month temperatures were much warmer than average statewide with all counties except Gila, above the 89^th percentile.

The 6-month precipitation was near average in six watersheds, and below average in eight watersheds. Only the Bill Williams watershed was wetter than average. Six month temperatures were above the 86^th percentile everywhere except the Colorado Plateau, though even plateau was above the 77^th percentile.

The 12-month period was near or slightly drier than normal with the near average conditions in the southeast watersheds including San Pedro, Santa Cruz and Willcox Playa, and the Little Colorado, Bill Williams and lower Gila. The driest watersheds were the Salt, lower Colorado and San Simon. The wettest watershed was at the 41^st percentile. The twelve month period was also very warm with all counties above the 80^th percentile, and the southern two-thirds of the state above the 85^th percentile.

The 24-month period is still the driest long-term interval after two back-to-back La Niña years. Thirteen watersheds were at or below the 20^th percentile and eight were at or below the 10^th percentile. Only the upper and Little Colorado watersheds had near average precipitation. The 24 month interval is still the warmest long term period with seven southern and southeastern counties above the 95^th percentile. Only Mohave County is below the 70^th percentile.

The 36-month period has eleven watersheds below the 22^nd percentile. The driest watersheds are in the southeast, though the Verde and Agua Fria are both below the 18^th percentile. The Upper and Little Colorado Basins are above the 43^rd percentile, largely due to the El Niño winter of 2010. Temperatures for the three year period were slightly warmer than average across the northern counties, and much warmer than average over the southern counties.

The 48-month period was very dry over the southern two-thirds of the state with the exceptions of the Salt and lower Gila watersheds which both had near average precipitation. Four watersheds in the southeast were below the 8^th percentile. Eleven counties in the southern half of the state were above the 85^th percentile.