State Precipitation & Temperature Update for Arizona

Conditions through September 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 10/17/2012. The data are preliminary.

Precipitation Percentiles by Watershed (through September 2012)

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Temperature Percentiles by Climate Division (through September 2012)

SHORT TERM CONDITIONS: 1-6 MONTHS

September, our last monsoon month was much wetter than normal across southern Arizona, near average in central Arizona, and much drier than normal in the northern watersheds. Temperatures were much warmer than normal in the western border counties as well as Maricopa and Pinal counties. The rest of the state had temperatures near average. The three month period, the monsoon, was by far the wettest short-term period with all watersheds except White Water Draw in the southeast above the 38^th percentile. Eleven watersheds were much wetter than normal, above the 66^th percentile, all in the northern 2/3 of the state. Temperatures for the summer were also much warmer than normal in the western counties and slightly warmer than normal in the eastern counties. Six month precipitation was greater than normal in the central and southwestern Arizona, and near normal across the rest of the state. Only White Water Draw in the southeast was slightly drier than normal. Six month temperatures were the highest of any interval both and short and long-term, above the 86^th percentile everywhere in the state, and above the 96^th percentile in the southern counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	19.05	CD1	92.37
Upper Colorado	19.05	CD2	72.03
Little Colorado	14.29	CD3	73.31
Verde	33.33	CD4	63.14
Bill Williams	28.57	CD5	90.68
Agua Fria	33.33	CD6	85.59
Lower Gila	88.10	CD7	68.64
Salt	38.10
Lower Colorado	73.81
Upper Gila	50.00
Santa Cruz	78.57
San Pedro	47.62
Willcox Playa	54.76
San Simon	90.48
White Water Draw	57.14

September 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	73.81	CD1	90.60
Upper Colorado	73.81	CD2	67.37
Little Colorado	66.67	CD3	84.75
Verde	80.95	CD4	84.32
Bill Williams	71.43	CD5	88.98
Agua Fria	78.57	CD6	88.98
Lower Gila	88.10	CD7	74.58
Salt	66.67
Lower Colorado	83.33
Upper Gila	71.43
Santa Cruz	50.00
San Pedro	69.05
Willcox Playa	38.10
San Simon	54.76
White Water Draw	29.27

July 2012 - September 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	54.76	CD1	90.60
Upper Colorado	54.76	CD2	86.44
Little Colorado	42.86	CD3	90.68
Verde	64.29	CD4	88.14
Bill Williams	64.29	CD5	97.46
Agua Fria	66.67	CD6	96.61
Lower Gila	85.71	CD7	98.31
Salt	61.90
Lower Colorado	80.95
Upper Gila	57.14
Santa Cruz	54.76
San Pedro	54.76
Willcox Playa	28.57
San Simon	57.14
White Water Draw	24.39

April 2011 – September 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 had near average precipitation in all but six watersheds, with the drier conditions across the northern and southeastern borders of the state. The twelve month period has been much warmer than normal, with all counties above the 79^th percentile, and the southern two-thirds of the state above the 86^th percentile.

The 24-month period is the driest of all intervals, representing the two back-to-back La Niña years. Six watersheds are at or below the 8^th percentile, while four others are below the 18^th percentile. Only three watersheds received near average precipitation. The 24 month temperatures were very warm with the southern half of the state above the 87^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	26.83	CD1	79.49
Upper Colorado	26.83	CD2	80.34
Little Colorado	31.71	CD3	86.32
Verde	31.71	CD4	82.05
Bill Williams	41.46	CD5	91.45
Agua Fria	41.46	CD6	88.89
Lower Gila	58.54	CD7	91.45
Salt	34.15
Lower Colorado	46.34
Upper Gila	36.59
Santa Cruz	26.83
San Pedro	29.27
Willcox Playa	22.50
San Simon	43.90
White Water Draw	26.83

October 2011 - September 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	45.00	CD1	71.55
Upper Colorado	45.00	CD2	75.00
Little Colorado	32.50	CD3	84.48
Verde	30.00	CD4	87.07
Bill Williams	17.50	CD5	87.93
Agua Fria	10.00	CD6	89.66
Lower Gila	25.00	CD7	94.83
Salt	12.50
Lower Colorado	25.00
Upper Gila	5.00
Santa Cruz	2.50
San Pedro	5.00
Willcox Playa	5.00
San Simon	7.50
White Water Draw	5.00

October 2010 – September 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 is the wettest long term interval, but only the Virgin and Upper Colorado watersheds received greater than normal precipitation. Nine watersheds were below the 30^th percentile, but only one was below the 8^th percentile. This reflects the wet El Niño winter of 2010. Temperatures for the three year period were the coolest of the long term intervals, with the northern counties below the 69^th percentile. The warmest counties in the southern third of Arizona were above the 89^th percentile.

The 48-month period was much drier than normal in the southeastern and central watersheds, and near average in the northern watersheds. Five watersheds were below the 8^th percentile, and five others had near average precipitation. Temperatures in the southern half of the state were above the 89^th percentile, except Yuma County which was at the 83^rd percentile along with Yavapai, Gila and the northeastern counties.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	64.10	CD1	70.43
Upper Colorado	64.10	CD2	68.70
Little Colorado	48.72	CD3	79.13
Verde	35.90	CD4	81.74
Bill Williams	25.64	CD5	83.48
Agua Fria	17.95	CD6	89.57
Lower Gila	48.72	CD7	91.30
Salt	28.21
Lower Colorado	46.15
Upper Gila	17.95
Santa Cruz	10.26
San Pedro	23.08
Willcox Playa	17.95
San Simon	7.69
White Water Draw	15.38

October 2009 - September 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	47.37	CD1	67.54
Upper Colorado	47.37	CD2	79.82
Little Colorado	34.21	CD3	83.33
Verde	18.42	CD4	83.33
Bill Williams	13.16	CD5	83.33
Agua Fria	13.16	CD6	98.25
Lower Gila	34.21	CD7	95.61
Salt	28.95
Lower Colorado	31.58
Upper Gila	13.16
Santa Cruz	2.63
San Pedro	7.89
Willcox Playa	7.89
San Simon	2.63
White Water Draw	5.26

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

October 2012 Arizona Drought Update (based on precipitation data through September 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

September, our last monsoon month was much wetter than normal across southern Arizona, near average in central Arizona, and much drier than normal in the northern watersheds. Temperatures were much warmer than normal in the western border counties as well as Maricopa and Pinal counties. The rest of the state had temperatures near average.

The 3-month period, the monsoon, was by far the wettest short-term period with all watersheds except White Water Draw in the southeast above the 38^th percentile. Eleven watersheds were much wetter than normal, above the 66^th percentile, all in the northern 2/3 of the state. Temperatures for the summer were also much warmer than normal in the western counties and slightly warmer than normal in the eastern counties.

The 6-month month precipitation was greater than normal in the central and southwestern Arizona, and near normal across the rest of the state. Only White Water Draw in the southeast was slightly drier than normal. Six month temperatures were the highest of any interval both and short and long-term, above the 86^th percentile everywhere in the state, and above the 96^th percentile in the southern counties.

The 12-month period had near average precipitation in all but six watersheds, with the drier conditions across the northern and southeastern borders of the state. The twelve month period has been much warmer than normal, with all counties above the 79^th percentile, and the southern two-thirds of the state above the 86^th percentile.

The 24-month period is the driest of all intervals, representing the two back-to-back La Niña years. Six watersheds are at or below the 8^th percentile, while four others are below the 18^th percentile. Only three watersheds received near average precipitation. The 24 month temperatures were very warm with the southern half of the state above the 87^th percentile.

The 36-month period is the wettest long term interval, but only the Virgin and Upper Colorado watersheds received greater than normal precipitation. Nine watersheds were below the 30^th percentile, but only one was below the 8^th percentile. This reflects the wet El Niño winter of 2010. Temperatures for the three year period were the coolest of the long term intervals, with the northern counties below the 69^th percentile. The warmest counties in the southern third of Arizona were above the 89^th percentile.

The 48-month period was much drier than normal in the southeastern and central watersheds, and near average in the northern watersheds. Five watersheds were below the 8^th percentile, and five others had near average precipitation. Temperatures in the southern half of the state were above the 89^th percentile, except Yuma County which was at the 83^rd percentile along with Yavapai, Gila and the northeastern counties.