State Precipitation & Temperature Update for Arizona

Conditions through October 2011

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 11/22/2011. The data are preliminary.

Precipitation Percentiles by Watershed (through October 2011)

v v

Temperature Percentiles by Climate Division (through October 2011)

SHORT TERM CONDITIONS: 1-6 MONTHS

October was wetter than average in the northern watersheds and near or slightly drier than average in the south, with Santa Cruz and San Pedro just below the 25^th percentile. October temperatures were somewhat warmer than average across the state between the 58^th and 92^nd percentiles. Maricopa and Pinal counties were warmest. The three month period was drier than average in all watersheds except the Little Colorado, White Water Draw, San Pedro and Willcox Playa in southeastern Arizona. Seven watersheds were below the 22^nd percentile. Temperatures in the three-month period were again much warmer than average, above the 86^th percentile in all counties. The southern counties were above the 98^th percentile. The six-month period was also much drier than average in the southern two thirds of the state. Six watersheds were below the 25^th percentile and four were near or wetter than average. Six month temperatures were slightly warmer than average in northern Arizona, and much warmer than average in the southern half of the state.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	63.41	CD1	76.92
Upper Colorado	60.98	CD2	58.12
Little Colorado	60.98	CD3	76.92
Verde	60.98	CD4	72.65
Bill Williams	56.10	CD5	89.74
Agua Fria	53.66	CD6	92.31
Lower Gila	46.34	CD7	90.60
Salt	41.46
Lower Colorado	32.93
Upper Gila	31.71
Santa Cruz	24.39
San Pedro	19.51
Willcox Playa	39.02
San Simon	36.59
White Water Draw	39.02

OCTOBER 2011: 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	38.46	CD1	86.21
Upper Colorado	31.71	CD2	88.03
Little Colorado	58.54	CD3	97.44
Verde	29.27	CD4	94.87
Bill Williams	17.07	CD5	98.29
Agua Fria	19.51	CD6	99.15
Lower Gila	21.95	CD7	99.15
Salt	17.07
Lower Colorado	7.32
Upper Gila	26.83
Santa Cruz	21.95
San Pedro	41.46
Willcox Playa	48.78
San Simon	17.07
White Water Draw	41.46

AUGUST 2011 - OCTOBER 2011 (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	56.41	CD1	62.93
Upper Colorado	48.78	CD2	59.83
Little Colorado	63.41	CD3	88.03
Verde	36.59	CD4	95.73
Bill Williams	7.32	CD5	86.32
Agua Fria	14.63	CD6	94.87
Lower Gila	26.83	CD7	95.73
Salt	29.27
Lower Colorado	17.07
Upper Gila	24.39
Santa Cruz	14.63
San Pedro	51.22
Willcox Playa	34.15
San Simon	4.88
White Water Draw	32.50

MAY 2011 – OCTOBER 2011 (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 remains the driest short-term period, with only one watershed, the upper Colorado, above the 40^th percentile. Eleven watersheds are below the 13^th percentile, with seven of those at or below the 5^th percentile. This reflects both the dry winter and the relatively dry monsoon. Temperatures were slightly warmer than average across the northern counties, and much warmer than average in the southern half of the state, where eleven counties were at or above the 80^th percentile.

The 24-month period is again the wettest long-term period with the Upper Colorado and Little Colorado much wetter than average, and five other watersheds near average. The driest watersheds were in southern Arizona, where the Santa Cruz and San Simon were below the 13^th percentile and the Willcox Playa and White Water Draw were both at the 20^th percentile. Temperatures on the Colorado Plateau were near average, while Mohave County was slightly warmer than average and the southern counties were all much warmer than average, above the 78^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	26.32	CD1	60.34
Upper Colorado	42.50	CD2	58.62
Little Colorado	40.00	CD3	81.90
Verde	20.00	CD4	90.52
Bill Williams	12.50	CD5	80.17
Agua Fria	5.00	CD6	87.07
Lower Gila	10.00	CD7	91.38
Salt	5.00
Lower Colorado	12.50
Upper Gila	5.00
Santa Cruz	2.50
San Pedro	5.00
Willcox Playa	5.13
San Simon	2.50
White Water Draw	5.00

NOVEMBER 2010 - OCTOBER 2011 (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	36.11	CD1	64.35
Upper Colorado	84.62	CD2	53.91
Little Colorado	64.10	CD3	80.87
Verde	48.72	CD4	81.74
Bill Williams	28.21	CD5	78.26
Agua Fria	28.21	CD6	88.70
Lower Gila	51.28	CD7	90.43
Salt	43.59
Lower Colorado	51.28
Upper Gila	25.64
Santa Cruz	12.82
San Pedro	41.03
Willcox Playa	20.51
San Simon	5.13
White Water Draw	20.51

NOVEMBER 2009 - OCTOBER 2011 (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 remains the driest long-term interval, with only the upper Colorado watershed above the 50^th percentile, while two others are above the 42^nd percentile. Nine watersheds are below the 24^th percentile and six of those are below the 14^th percentile. Temperatures for the three year period were warmer than average everywhere, with the four northern counties between the 67^th and 73^rd percentiles. Gila, La Paz, Yuma, and Yavapai counties were all near the 83^rd percentile. Maricopa and Pinal, plus the seven south and southeastern counties, were all above the 94^th percentile.

The 48-month period is a patchwork of wet and dry watersheds. Two watersheds (Upper Colorado and Lower Gila) continue to be wetter than average (above the 64^th percentile) and three (Virgin, White Water Draw, and Santa Cruz) remain much drier than average (below the 15^th percentile). Five others in central and southeastern Arizona are below the 22^nd percentile. The pattern of wet and dry watersheds reflects the varying storm tracks during the past four winters. In the two La Niña winters (2008, 2011), storms tracked across northern Arizona, leaving much of southern Arizona dry; while during the El Niño winter (2010) and the neutral winter (2009), the storms tracked across the southern counties. Eastern Arizona has enjoyed more frequent precipitation during both El Niño and La Niña winters, while western Arizona had fewer storms tracks. Temperatures for the four year period continue to be warmer than average in all counties, with Maricopa and Pinal above the 98^th percentile. The seven southeastern counties are above the 89^th percentile.

Watershed	Precipitation Percentile	Climate Division	Temperature Percentile
Virgin	27.78	CD1	67.54
Upper Colorado	65.79	CD2	72.81
Little Colorado	44.74	CD3	81.58
Verde	23.68	CD4	82.46
Bill Williams	21.05	CD5	83.33
Agua Fria	15.79	CD6	95.61
Lower Gila	36.84	CD7	94.74
Salt	42.11
Lower Colorado	36.84
Upper Gila	13.16
Santa Cruz	2.63
San Pedro	13.16
Willcox Playa	13.16
San Simon	2.63
White Water Draw	10.53

NOVEMBER 2008 - OCTOBER 2011 (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	14.71	CD1	66.37
Upper Colorado	72.97	CD2	74.78
Little Colorado	45.95	CD3	81.42
Verde	21.62	CD4	78.76
Bill Williams	18.92	CD5	82.30
Agua Fria	13.51	CD6	98.23
Lower Gila	64.86	CD7	89.38
Salt	56.76
Lower Colorado	29.73
Upper Gila	29.73
Santa Cruz	5.41
San Pedro	32.43
Willcox Playa	16.22
San Simon	16.22
White Water Draw	16.22

NOVEMBER 2007 - OCTOBER 2011 (48-month): percentiles of precipitation for the 15 Arizona watersheds and percentiles of temperature for the 7 climate divisions.

November 2011 Arizona Drought Update (based on precipitation data through October 2011)

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

SUMMARY

October was wetter than average in the northern watersheds and near or slightly drier than average in the south, with Santa Cruz and San Pedro just below the 25^th percentile. October temperatures were somewhat warmer than average across the state between the 58^th and 92^nd percentiles. Maricopa and Pinal counties were warmest.

The 3-month period was drier than average in all watersheds except the Little Colorado, White Water Draw, San Pedro and Willcox Playa in southeastern Arizona. Seven watersheds were below the 22^nd percentile. Temperatures in the three-month period were again much warmer than average, above the 86^th percentile in all counties. The southern counties were above the 98^th percentile.

The 6-month period was also much drier than average in the southern two thirds of the state. Six watersheds were below the 25^th percentile and four were near or wetter than average. Six month temperatures were slightly warmer than average in northern Arizona, and much warmer than average in the southern half of the state.

The 12-month period remains the driest short-term period, with only one watershed, the upper Colorado, above the 40^th percentile. Eleven watersheds are below the 13^th percentile, with seven of those at or below the 5^th percentile. This reflects both the dry winter and the relatively dry monsoon. Temperatures were slightly warmer than average across the northern counties, and much warmer than average in the southern half of the state, where eleven counties were at or above the 80^th percentile.

The 24-month period is again the wettest long-term period with the Upper Colorado and Little Colorado much wetter than average, and five other watersheds near average. The driest watersheds were in southern Arizona, where the Santa Cruz and San Simon were below the 13^th percentile and the Willcox Playa and White Water Draw were both at the 20^th percentile. Temperatures on the Colorado Plateau were near average, while Mohave County was slightly warmer than average and the southern counties were all much warmer than average, above the 78^th percentile.

The 36-month period remains the driest long-term interval, with only the upper Colorado watershed above the 50^th percentile, while two others are above the 42^nd percentile. Nine watersheds are below the 24^th percentile and six of those are below the 14^th percentile. Temperatures for the three year period were warmer than average everywhere, with the four northern counties between the 67^th and 73^rd percentiles. Gila, La Paz, Yuma, and Yavapai counties were all near the 83^rd percentile. Maricopa and Pinal, plus the seven south and southeastern counties, were all above the 94^th percentile.

The 48-month period is a patchwork of wet and dry watersheds. Two watersheds (Upper Colorado and Lower Gila) continue to be wetter than average (above the 64^th percentile) and three (Virgin, White Water Draw, and Santa Cruz) remain much drier than average (below the 15^th percentile). Five others in central and southeastern Arizona are below the 22^nd percentile. The pattern of wet and dry watersheds reflects the varying storm tracks during the past four winters. In the two La Niña winters (2008, 2011), storms tracked across northern Arizona, leaving much of southern Arizona dry; while during the El Niño winter (2010) and the neutral winter (2009), the storms tracked across the southern counties. Eastern Arizona has enjoyed more frequent precipitation during both El Niño and La Niña winters, while western Arizona had fewer storms tracks. Temperatures for the four year period continue to be warmer than average in all counties, with Maricopa and Pinal above the 98^th percentile. The seven southeastern counties are above the 89^th percentile.